top (1)

Contents

NAME
SYNOPSIS
DESCRIPTION
OVERVIEW
Documentation
Operation
Startup Defaults
1. COMMAND-LINE Options
2. SUMMARY Display
2a. UPTIME and LOAD Averages
2b. TASK and CPU States
2c. MEMORY Usage
3. FIELDS / Columns
3a. DESCRIPTIONS of Fields
3b. MANAGING Fields
4. INTERACTIVE Commands
4a. GLOBAL Commands
4b. SUMMARY AREA Commands
4c. TASK AREA Commands
4d. COLOR Mapping
5. ALTERNATE-DISPLAY Provisions
5a. WINDOWS Overview
5b. COMMANDS for Windows
5c. SCROLLING a Window
5d. SEARCHING in a Window
5e. FILTERING in a Window
6. FILES
6a. SYSTEM Configuration File
6b. PERSONAL Configuration File
6c. ADDING INSPECT Entries
7. STUPID TRICKS Sampler
7a. Kernel Magic
7b. Bouncing Windows
7c. The Big Bird Window
7d. The Ol' Switcheroo
8. BUGS
9. HISTORY Former top
10. AUTHOR
11. SEE Also

NAME

top - display Linux processes

SYNOPSIS

top -hv|-bcHiOSs -d secs -n max -u|U user -p pid -o fld -w [cols]

The traditional switches '-' and whitespace are optional.

DESCRIPTION

The top program provides a dynamic real-time view of a running system. It can display system summary information as well as a list of processes or threads currently being managed by the Linux kernel. The types of system summary information shown and the types, order and size of information displayed for processes are all user configurable and that configuration can be made persistent across restarts.

The program provides a limited interactive interface for process manipulation as well as a much more extensive interface for personal configuration  --  encompassing every aspect of its operation. And while top is referred to throughout this document, you are free to name the program anything you wish. That new name, possibly an alias, will then be reflected on top's display and used when reading and writing a configuration file.

OVERVIEW

Documentation

The remaining Table of Contents 

    1. COMMAND-LINE Options
    2. SUMMARY Display
       a. UPTIME and LOAD Averages
       b. TASK and CPU States
       c. MEMORY Usage
    3. FIELDS / Columns Display
       a. DESCRIPTIONS of Fields
       b. MANAGING Fields
    4. INTERACTIVE Commands
       a. GLOBAL Commands
       b. SUMMARY AREA Commands
       c. TASK AREA Commands
          1. Appearance
          2. Content
          3. Size
          4. Sorting
       d. COLOR Mapping
    5. ALTERNATE-DISPLAY Provisions
       a. WINDOWS Overview
       b. COMMANDS for Windows
       c. SCROLLING a Window
       d. SEARCHING in a Window
       e. FILTERING in a Window
    6. FILES
       a. SYSTEM Configuration File
       b. PERSONAL Configuration File
       c. ADDING INSPECT Entries
    7. STUPID TRICKS Sampler
       a. Kernel Magic
       b. Bouncing Windows
       c. The Big Bird Window
       d. The Ol' Switcheroo
    8. BUGS, 9. HISTORY Former top, 10. AUTHOR, 11. SEE Also

Operation

When operating top, the two most important keys are the help ('h' or '?') key and quit ('q') key. Alternatively, you could simply use the traditional interrupt key ('^C') when you're done.

When started for the first time, you'll be presented with these traditional elements on the main top screen: 1) Summary Area; 2) Fields/Columns Header; 3) Task Area. Each of these will be explored in the sections that follow. There is also an Input/Message line between the Summary Area and Columns Header which needs no further explanation.

The main top screen is generally quite adaptive to changes in terminal dimensions under X-Windows. Other top screens may be less so, especially those with static text. It ultimately depends, however, on your particular window manager and terminal emulator. There may be occasions when their view of terminal size and current contents differs from top's view, which is always based on operating system calls.

Following any re-size operation, if a top screen is corrupted, appears incomplete or disordered, simply typing something innocuous like a punctuation character or cursor motion key will usually restore it. In extreme cases, the following sequence almost certainly will: 

       key/cmd  objective 
       ^Z       suspend top
       fg       resume top
       <Left>   force a screen redraw (if necessary)

But if the display is still corrupted, there is one more step you could try. Insert this command after top has been suspended but before resuming it. 

       key/cmd  objective 
       reset    restore your terminal settings

Note: the width of top's display will be limited to 512 positions. Displaying all fields requires approximately 250 characters. Remaining screen width is usually allocated to any variable width columns currently visible. The variable width columns, such as COMMAND, are noted in topic 3a. DESCRIPTIONS of Fields. Actual output width may also be influenced by the -w switch, which is discussed in topic 1. COMMAND-LINE Options.

Lastly, some of top's screens or functions require the use of cursor motion keys like the standard arrow keys plus the Home, End, PgUp and PgDn keys. If your terminal or emulator does not provide those keys, the following combinations are accepted as alternatives: 

       key      equivalent-key-combinations 
       Up       alt + \      or  alt + k 
       Down     alt + /      or  alt + j 
       Left     alt + <      or  alt + h 
       Right    alt + >      or  alt + l (lower case L)
       PgUp     alt + Up     or  alt + ctrl + k 
       PgDn     alt + Down   or  alt + ctrl + j 
       Home     alt + Left   or  alt + ctrl + h 
       End      alt + Right  or  alt + ctrl + l

The Up and Down arrow keys have special significance when prompted for line input terminated with the <Enter> key. Those keys, or their aliases, can be used to retrieve previous input lines which can then be edited and re-input. And there are four additional keys available with line oriented input. 

       key      special-significance 
       Up       recall older strings for re-editing
       Down     recall newer strings or erase entire line
       Insert   toggle between insert and overtype modes
       Delete   character removed at cursor, moving others left
       Home     jump to beginning of input line
       End      jump to end of input line

Startup Defaults

The following startup defaults assume no configuration file, thus no user customizations. Even so, items shown with an asterisk ('*') could be overridden through the command-line. All are explained in detail in the sections that follow. 

    Global-defaults
       'A' - Alt display      Off (full-screen)
     * 'd' - Delay time       3.0 seconds
     * 'H' - Threads mode     Off (summarize as tasks)
       'I' - Irix mode        On  (no, 'solaris' smp)
     * 'p' - PID monitoring   Off (show all processes)
     * 's' - Secure mode      Off (unsecured)
       'B' - Bold enable      On  (yes, bold globally)
    Summary-Area-defaults
       'l' - Load Avg/Uptime  On  (thus program name)
       't' - Task/Cpu states  On  (1+1 lines, see '1')
       'm' - Mem/Swap usage   On  (2 lines worth)
       '1' - Single Cpu       On  (thus 1 line if smp)
    Task-Area-defaults
       'b' - Bold hilite      On  (not 'reverse')
     * 'c' - Command line     Off (name, not cmdline)
     * 'i' - Idle tasks       On  (show all tasks)
       'J' - Num align right  On  (not left justify)
       'j' - Str align right  Off (not right justify)
       'R' - Reverse sort     On  (pids high-to-low)
     * 'S' - Cumulative time  Off (no, dead children)
     * 'u' - User filter      Off (show euid only)
     * 'U' - User filter      Off (show any uid)
       'x' - Column hilite    Off (no, sort field)
       'y' - Row hilite       On  (yes, running tasks)
       'z' - color/mono       Off (no, colors)

1. COMMAND-LINE Options

The command-line syntax for top consists of:


  -hv|-bcHiOSs -d secs -n max -u|U user -p pid -o fld -w [cols]

The typically mandatory switches ('-') and even whitespace are completely optional.

-h | -v  :Help/Version
Show library version and the usage prompt, then quit.

-b  :Batch-mode operation
Starts top in 'Batch' mode, which could be useful for sending output from top to other programs or to a file. In this mode, top will not accept input and runs until the iterations limit you've set with the '-n' command-line option or until killed.

-c  :Command-line/Program-name toggle
Starts top with the last remembered 'c' state reversed. Thus, if top was displaying command lines, now that field will show program names, and visa versa. See the 'c' interactive command for additional information.

-d  :Delay-time interval as:  -d ss.t (secs.tenths)
Specifies the delay between screen updates, and overrides the corresponding value in one's personal configuration file or the startup default. Later this can be changed with the 'd' or 's' interactive commands.

Fractional seconds are honored, but a negative number is not allowed. In all cases, however, such changes are prohibited if top is running in 'Secure mode', except for root (unless the 's' command-line option was used). For additional information on 'Secure mode' see topic 6a. SYSTEM Configuration File.

-H  :Threads-mode operation
Instructs top to display individual threads. Without this command-line option a summation of all threads in each process is shown. Later this can be changed with the 'H' interactive command.

-i  :Idle-process toggle
Starts top with the last remembered 'i' state reversed. When this toggle is Off, tasks that have not used any CPU since the last update will not be displayed. For additional information regarding this toggle see topic 4c. TASK AREA Commands, SIZE.

-n  :Number-of-iterations limit as:  -n number
Specifies the maximum number of iterations, or frames, top should produce before ending.

-o  :Override-sort-field as:  -o fieldname
Specifies the name of the field on which tasks will be sorted, independent of what is reflected in the configuration file. You can prepend a '+' or '-' to the field name to also override the sort direction. A leading '+' will force sorting high to low, whereas a '-' will ensure a low to high ordering.

This option exists primarily to support automated/scripted batch mode operation.

-O  :Output-field-names
This option acts as a form of help for the above -o option. It will cause top to print each of the available field names on a separate line, then quit. Such names are subject to nls translation.

-p  :Monitor-PIDs mode as:  -pN1 -pN2 ...  or  -pN1,N2,N3 ...
Monitor only processes with specified process IDs. This option can be given up to 20 times, or you can provide a comma delimited list with up to 20 pids. Co-mingling both approaches is permitted.

A pid value of zero will be treated as the process id of the top program itself once it is running.

This is a command-line option only and should you wish to return to normal operation, it is not necessary to quit and restart top  --  just issue any of these interactive commands: '=', 'u' or 'U'.

The 'p', 'u' and 'U' command-line options are mutually exclusive.

-s  :Secure-mode operation
Starts top with secure mode forced, even for root. This mode is far better controlled through the system configuration file (see topic 6. FILES).

-S  :Cumulative-time toggle
Starts top with the last remembered 'S' state reversed. When 'Cumulative time' mode is On, each process is listed with the cpu time that it and its dead children have used. See the 'S' interactive command for additional information regarding this mode.

-u | -U  :User-filter-mode as:  -u | -U number or name
Display only processes with a user id or user name matching that given. The '-u' option matches on effective user whereas the '-U' option matches on any user (real, effective, saved, or filesystem).

Prepending an exclamation point ('!') to the user id or name instructs top to display only processes with users not matching the one provided.

The 'p', 'u' and 'U' command-line options are mutually exclusive.

-w  :Output-width-override as:  -w [ number ]
In 'Batch' mode, when used without an argument top will format output using the COLUMNS= and LINES= environment variables, if set. Otherwise, width will be fixed at the maximum 512 columns. With an argument, output width can be decreased or increased (up to 512) but the number of rows is considered unlimited.

In normal display mode, when used without an argument top will attempt to format output using the COLUMNS= and LINES= environment variables, if set. With an argument, output width can only be decreased, not increased. Whether using environment variables or an argument with -w, when not in 'Batch' mode actual terminal dimensions can never be exceeded.

Note: Without the use of this command-line option, output width is always based on the terminal at which top was invoked whether or not in 'Batch' mode.

2. SUMMARY Display

Each of the following three areas are individually controlled through one or more interactive commands. See topic 4b. SUMMARY AREA Commands for additional information regarding these provisions.

2a. UPTIME and LOAD Averages

This portion consists of a single line containing: 
    program or window name, depending on display mode
    current time and length of time since last boot
    total number of users
    system load avg over the last 1, 5 and 15 minutes

2b. TASK and CPU States

This portion consists of a minimum of two lines. In an SMP environment, additional lines can reflect individual CPU state percentages.

Line 1 shows total tasks or threads, depending on the state of the Threads-mode toggle. That total is further classified as: 

    running; sleeping; stopped; zombie

Line 2 shows CPU state percentages based on the interval since the last refresh. Where two labels are shown below, those for more recent kernel versions are shown first. 

    us, user    : time running un-niced user processes
    sy, system  : time running kernel processes
    ni, nice    : time running niced user processes
    wa, IO-wait : time waiting for I/O completion
    hi : time spent servicing hardware interrupts
    si : time spent servicing software interrupts
    st : time stolen from this vm by the hypervisor

2c. MEMORY Usage

This portion consists of two lines which may express values in kibibytes (KiB) through exbibytes (EiB) depending on the scaling factor enforced with the 'E' interactive command.

Line 1 reflects physical memory, classified as: 

    total, used, free and buffers

Line 2 reflects mostly virtual memory, classified as: 

    total, used, free and cached (which is physical memory)

This table may help in interpreting the scaled values displayed: 

    KiB = kibibyte = 1024 bytes
    MiB = mebibyte = 1024 KiB = 1,048,576 bytes
    GiB = gibibyte = 1024 MiB = 1,073,741,824 bytes
    TiB = tebibyte = 1024 GiB = 1,099,511,627,776 bytes
    PiB = pebibyte = 1024 TiB = 1,125,899,906,842,624 bytes
    EiB = exbibyte = 1024 PiB = 1,152,921,504,606,846,976 bytes

3. FIELDS / Columns

3a. DESCRIPTIONS of Fields

Listed below are top's available process fields (columns). They are shown in strict ascii alphabetical order. You may customize their position and whether or not they are displayable with the 'f' or 'F' (Fields Management) interactive commands.

Any field is selectable as the sort field, and you control whether they are sorted high-to-low or low-to-high. For additional information on sort provisions see topic 4c. TASK AREA Commands, SORTING.

The fields related to physical memory or virtual memory reference '(KiB)' as the default, unsuffixed display mode. Such fields can, however, be scaled differently via the 'e' interactive command.


 1. %CPU  --  CPU Usage 
The task's share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.

In a true SMP environment, if a process is multi-threaded and top is not operating in Threads mode, amounts greater than 100% may be reported. You toggle Threads mode with the 'H' interactive command.

Also for multi-processor environments, if 'Irix mode' is Off, top will operate in 'Solaris mode' where a task's cpu usage will be divided by the total number of CPUs. You toggle 'Irix/Solaris' modes with the 'I' interactive command.


 2. %MEM  --  Memory Usage (RES) 
A task's currently used share of available physical memory.


 3. CGROUPS  --  Control Groups 
The names of the control group(s) to which a process belongs, or '-' if not applicable for that process.

Control Groups provide for allocating resources (cpu, memory, network bandwidth, etc.) among installation-defined groups of processes. They enable fine-grained control over allocating, denying, prioritizing, managing and monitoring those resources.

Many different hierarchies of cgroups can exist simultaneously on a system and each hierarchy is attached to one or more subsystems. A subsystem represents a single resource.

Note: The 'CGROUPS' field, unlike most columns, is not fixed-width. When displayed, it plus any other variable width columns will be allocated all remaining screen width (up to the maximum 512 characters). Even so, such variable width fields could still suffer truncation. See topic 5c. SCROLLING a Window for additional information on accessing any truncated data.


 4. CODE  --  Code Size (KiB) 
The amount of physical memory devoted to executable code, also known as the 'text resident set' size or TRS.


 5. COMMAND  --  Command Name or Command Line 
Display the command line used to start a task or the name of the associated program. You toggle between command line and name with 'c', which is both a command-line option and an interactive command.

When you've chosen to display command lines, processes without a command line (like kernel threads) will be shown with only the program name in brackets, as in this example:
    [kthreadd]

This field may also be impacted by the 'forest view' display mode. See the 'V' interactive command for additional information regarding that mode.

Note: The 'COMMAND' field, unlike most columns, is not fixed-width. When displayed, it plus any other variable width columns will be allocated all remaining screen width (up to the maximum 512 characters). Even so, such variable width fields could still suffer truncation. This is especially true for this field when command lines are being displayed (the 'c' interactive command.) See topic 5c. SCROLLING a Window for additional information on accessing any truncated data.


 6. DATA  --  Data + Stack Size (KiB) 
The amount of physical memory devoted to other than executable code, also known as the 'data resident set' size or DRS.


 7. ENVIRON  --  Environment variables 
Display all of the environment variables, if any, as seen by the respective processes. These variables will be displayed in their raw native order, not the sorted order you are accustomed to seeing with an unqualified 'set'.

Note: The 'ENVIRON' field, unlike most columns, is not fixed-width. When displayed, it plus any other variable width columns will be allocated all remaining screen width (up to the maximum 512 characters). Even so, such variable width fields could still suffer truncation. This is especially true for this field. See topic 5c. SCROLLING a Window for additional information on accessing any truncated data.


 8. Flags  --  Task Flags 
This column represents the task's current scheduling flags which are expressed in hexadecimal notation and with zeros suppressed. These flags are officially documented in <linux/sched.h>.


 9. GID  --  Group Id 
The effective group ID.

10. GROUP  --  Group Name
The effective group name.

11. NI  --  Nice Value
The nice value of the task. A negative nice value means higher priority, whereas a positive nice value means lower priority. Zero in this field simply means priority will not be adjusted in determining a task's dispatch-ability.

12. P  --  Last used CPU (SMP)
A number representing the last used processor. In a true SMP environment this will likely change frequently since the kernel intentionally uses weak affinity. Also, the very act of running top may break this weak affinity and cause more processes to change CPUs more often (because of the extra demand for cpu time).

13. PGRP  --  Process Group Id
Every process is member of a unique process group which is used for distribution of signals and by terminals to arbitrate requests for their input and output. When a process is created (forked), it becomes a member of the process group of its parent. By convention, this value equals the process ID (see PID) of the first member of a process group, called the process group leader.

14. PID  --  Process Id
The task's unique process ID, which periodically wraps, though never restarting at zero. In kernel terms, it is a dispatchable entity defined by a 'task_struct'.

This value may also be used as: a process group ID (see PGRP); a session ID for the session leader (see SID); a thread group ID for the thread group leader (see TGID); and a TTY process group ID for the process group leader (see TPGID).

15. PPID  --  Parent Process Id
The process ID (pid) of a task's parent.

16. PR  --  Priority
The scheduling priority of the task. If you see 'rt' in this field, it means the task is running under 'real time' scheduling priority.

Under linux, real time priority is somewhat misleading since traditionally the operating itself was not preemptible. And while the 2.6 kernel can be made mostly preemptible, it is not always so.

17. RES  --  Resident Memory Size (KiB)
The non-swapped physical memory a task has used.

18. RUID  --  Real User Id
The real user ID.

19. RUSER  --  Real User Name
The real user name.

20. S  --  Process Status
The status of the task which can be one of:
    D = uninterruptible sleep
    R = running
    S = sleeping
    T = traced or stopped
    Z = zombie

Tasks shown as running should be more properly thought of as 'ready to run'  --  their task_struct is simply represented on the Linux run-queue. Even without a true SMP machine, you may see numerous tasks in this state depending on top's delay interval and nice value.

21. SHR  --  Shared Memory Size (KiB)
The amount of shared memory available to a task, not all of which is typically resident. It simply reflects memory that could be potentially shared with other processes.

22. SID  --  Session Id
A session is a collection of process groups (see PGRP), usually established by the login shell. A newly forked process joins the session of its creator. By convention, this value equals the process ID (see PID) of the first member of the session, called the session leader, which is usually the login shell.

23. SUID  --  Saved User Id
The saved user ID.

24. SUPGIDS  --  Supplementary Group IDs
The IDs of any supplementary group(s) established at login or inherited from a task's parent. They are displayed in a comma delimited list.

Note: The 'SUPGIDS' field, unlike most columns, is not fixed-width. When displayed, it plus any other variable width columns will be allocated all remaining screen width (up to the maximum 512 characters). Even so, such variable width fields could still suffer truncation. See topic 5c. SCROLLING a Window for additional information on accessing any truncated data.

25. SUPGRPS  --  Supplementary Group Names
The names of any supplementary group(s) established at login or inherited from a task's parent. They are displayed in a comma delimited list.

Note: The 'SUPGRPS' field, unlike most columns, is not fixed-width. When displayed, it plus any other variable width columns will be allocated all remaining screen width (up to the maximum 512 characters). Even so, such variable width fields could still suffer truncation. See topic 5c. SCROLLING a Window for additional information on accessing any truncated data.

26. SUSER  --  Saved User Name
The saved user name.

27. SWAP  --  Swapped Size (KiB)
The non-resident portion of a task's address space.

28. TGID  --  Thread Group Id
The ID of the thread group to which a task belongs. It is the PID of the thread group leader. In kernel terms, it represents those tasks that share an 'mm_struct'.

29. TIME  --  CPU Time
Total CPU time the task has used since it started. When 'Cumulative mode' is On, each process is listed with the cpu time that it and its dead children have used. You toggle 'Cumulative mode' with 'S', which is both a command-line option and an interactive command. See the 'S' interactive command for additional information regarding this mode.

30. TIME+  --  CPU Time, hundredths
The same as 'TIME', but reflecting more granularity through hundredths of a second.

31. TPGID  --  Tty Process Group Id
The process group ID of the foreground process for the connected tty, or -1 if a process is not connected to a terminal. By convention, this value equals the process ID (see PID) of the process group leader (see PGRP).

32. TTY  --  Controlling Tty
The name of the controlling terminal. This is usually the device (serial port, pty, etc.) from which the process was started, and which it uses for input or output. However, a task need not be associated with a terminal, in which case you'll see '?' displayed.

33. UID  --  User Id
The effective user ID of the task's owner.

34. USED  --  Memory in Use (KiB)
This field represents the non-swapped physical memory a task has used (RES) plus the non-resident portion of its address space (SWAP).

35. USER  --  User Name
The effective user name of the task's owner.

36. VIRT  --  Virtual Memory Size (KiB)
The total amount of virtual memory used by the task. It includes all code, data and shared libraries plus pages that have been swapped out and pages that have been mapped but not used.

37. WCHAN  --  Sleeping in Function
Depending on the availability of the kernel link map ('System.map'), this field will show the name or the address of the kernel function in which the task is currently sleeping. Running tasks will display a dash ('-') in this column.

By displaying this field, top's own working set could be increased by over 700Kb, depending on the kernel version. Should that occur, your only means of reducing that overhead will be to stop and restart top.

38. nDRT  --  Dirty Pages Count
The number of pages that have been modified since they were last written to auxiliary storage. Dirty pages must be written to auxiliary storage before the corresponding physical memory location can be used for some other virtual page.

39. nMaj  --  Major Page Fault Count
The number of major page faults that have occurred for a task. A page fault occurs when a process attempts to read from or write to a virtual page that is not currently present in its address space. A major page fault is when auxiliary storage access is involved in making that page available.

40. nMin  --  Minor Page Fault count
The number of minor page faults that have occurred for a task. A page fault occurs when a process attempts to read from or write to a virtual page that is not currently present in its address space. A minor page fault does not involve auxiliary storage access in making that page available.

41. nTH  --  Number of Threads
The number of threads associated with a process.

42. nsIPC  --  IPC namespace
The Inode of the namespace used to isolate interprocess communication (IPC) resources such as System V IPC objects and POSIX message queues.

43. nsMNT  --  MNT namespace
The Inode of the namespace used to isolate filesystem mount points thus offering different views of the filesystem hierarchy.

44. nsNET  --  NET namespace
The Inode of the namespace used to isolate resources such as network devices, IP addresses, IP routing, port numbers, etc.

45. nsPID  --  PID namespace
The Inode of the namespace used to isolate process ID numbers meaning they need not remain unique. Thus, each such namespace could have its own 'init' (PID #1) to manage various initialization tasks and reap orphaned child processes.

46. nsUSER  --  USER namespace
The Inode of the namespace used to isolate the user and group ID numbers. Thus, a process could have a normal unprivileged user ID outside a user namespace while having a user ID of 0, with full root privileges, inside that namespace.

47. nsUTS  --  UTS namespace
The Inode of the namespace used to isolate hostname and NIS domain name. UTS simply means "UNIX Time-sharing System".

48. vMj  --  Major Page Fault Count Delta
The number of major page faults that have occurred since the last update (see nMaj).

49. vMn  --  Minor Page Fault Count Delta
The number of minor page faults that have occurred since the last update (see nMin).

3b. MANAGING Fields

After pressing the interactive command 'f' or 'F' (Fields Management) you will be presented with a screen showing: 1) the 'current' window name; 2) the designated sort field; 3) all fields in their current order along with descriptions. Entries marked with an asterisk are the currently displayed fields, screen width permitting.

o
As the on screen instructions indicate, you navigate among the fields with the Up and Down arrow keys. The PgUp, PgDn, Home and End keys can also be used to quickly reach the first or last available field.

o
The Right arrow key selects a field for repositioning and the Left arrow key or the <Enter> key commits that field's placement.

o
The 'd' key or the <Space> bar toggles a field's display status, and thus the presence or absence of the asterisk.

o
The 's' key designates a field as the sort field. See topic 4c. TASK AREA Commands, SORTING for additional information regarding your selection of a sort field.

o
The 'a' and 'w' keys can be used to cycle through all available windows and the 'q' or <Esc> keys exit Fields Management.

The Fields Management screen can also be used to change the 'current' window/field group in either full-screen mode or alternate-display mode. Whatever was targeted when 'q' or <Esc> was pressed will be made current as you return to the top display. See topic 5. ALTERNATE-DISPLAY Provisions and the 'g' interactive command for insight into 'current' windows and field groups.

Note: Any window that has been scrolled horizontally will be reset if any field changes are made via the Fields Management screen. Any vertical scrolled position, however, will not be affected. See topic 5c. SCROLLING a Window for additional information regarding vertical and horizontal scrolling.

4. INTERACTIVE Commands

Listed below is a brief index of commands within categories. Some commands appear more than once  --  their meaning or scope may vary depending on the context in which they are issued. 

  4a. Global-Commands 
        <Ent/Sp> ?, =, 0,
        A, B, d, E, e, g, h, H, I, k, q, r, s, W, X, Y, Z
  4b. Summary-Area-Commands 
        C, l, t, m, 1, 2, 3
  4c. Task-Area-Commands 
        Appearance:  b, J, j, x, y, z
        Content:     c, f, F, o, O, S, u, U, V
        Size:        #, i, n
        Sorting:     <, >, f, F, R
  4d. Color-Mapping 
        <Ret>, a, B, b, H, M, q, S, T, w, z, 0 - 7
  5b. Commands-for-Windows 
        -, _, =, +, A, a, g, G, w
  5c. Scrolling-a-Window 
        C, Up, Dn, Left, Right, PgUp, PgDn, Home, End
  5d. Searching-in-a-Window 
        L, &

4a. GLOBAL Commands

The global interactive commands are always available in both full-screen mode and alternate-display mode. However, some of these interactive commands are not available when running in 'Secure mode'.

If you wish to know in advance whether or not your top has been secured, simply ask for help and view the system summary on the second line.

  <Enter> or <Space>  :Refresh-Display
These commands awaken top and following receipt of any input the entire display will be repainted. They also force an update of any hotplugged cpu or physical memory changes.

Use either of these keys if you have a large delay interval and wish to see current status,

   ? | h  :Help
There are two help levels available. The first will provide a reminder of all the basic interactive commands. If top is secured, that screen will be abbreviated.

Typing 'h' or '?' on that help screen will take you to help for those interactive commands applicable to alternate-display mode.

   =  :Exit-Task-Limits
Removes restrictions on which tasks are shown. This command will reverse any 'i' (idle tasks) and 'n' (max tasks) commands that might be active. It also provides for an exit from pid monitoring, 'user' filtering and 'other' filtering. See the '-p' command-line option for a discussion of PID monitoring, the 'U' or 'u' interactive commands for user filtering and the 'O' or 'o' interactive commands for 'other' filtering.

Additionally, any window that has been scrolled will be reset with this command. See topic 5c. SCROLLING a Window for additional information regarding vertical and horizontal scrolling.

When operating in alternate-display mode this command has a broader meaning.

   0  :Zero-Suppress toggle
This command determines whether zeros are shown or suppressed for many of the fields in a task window. Fields like UID, GID, NI, PR or P are not affected by this toggle.

   A  :Alternate-Display-Mode toggle
This command will switch between full-screen mode and alternate-display mode. See topic 5. ALTERNATE-DISPLAY Provisions and the 'g' interactive command for insight into 'current' windows and field groups.

   B  :Bold-Disable/Enable toggle
This command will influence use of the 'bold' terminfo capability and alters both the summary area and task area for the 'current' window. While it is intended primarily for use with dumb terminals, it can be applied anytime.

Note: When this toggle is On and top is operating in monochrome mode, the entire display will appear as normal text. Thus, unless the 'x' and/or 'y' toggles are using reverse for emphasis, there will be no visual confirmation that they are even on.

*  d | s  :Change-Delay-Time-interval
You will be prompted to enter the delay time, in seconds, between display updates.

Fractional seconds are honored, but a negative number is not allowed. Entering 0 causes (nearly) continuous updates, with an unsatisfactory display as the system and tty driver try to keep up with top's demands. The delay value is inversely proportional to system loading, so set it with care.

If at any time you wish to know the current delay time, simply ask for help and view the system summary on the second line.

   E  :Extend-Memory-Scale in Summary Area
With this command you can cycle through the available summary area memory scaling which ranges from KiB (kibibytes or 1,024 bytes) through EiB (exbibytes or 1,152,921,504,606,846,976 bytes).

If you see a '+' between a displayed number and the following label, it means that top was forced to truncate some portion of that number. By raising the scaling factor, such truncation can be avoided.

   e  :Extend-Memory-Scale in Task Windows
With this command you can cycle through the available task window memory scaling which ranges from KiB (kibibytes or 1,024 bytes) through PiB (pebibytes or 1,125,899,906,842,624 bytes).

While top will try to honor the selected target range, additional scaling might still be necessary in order to accommodate current values. If you wish to see a more homogeneous result in the memory columns, raising the scaling range will usually accomplish that goal. Raising it too high, however, is likely to produce an all zero result which cannot be suppressed with the '0' interactive command.

   g  :Choose-Another-Window/Field-Group
You will be prompted to enter a number between 1 and 4 designating the field group which should be made the 'current' window. You will soon grow comfortable with these 4 windows, especially after experimenting with alternate-display mode.

   H  :Threads-mode toggle
When this toggle is On, individual threads will be displayed for all processes in all visible task windows. Otherwise, top displays a summation of all threads in each process.

   I  :Irix/Solaris-Mode toggle
When operating in 'Solaris mode' ('I' toggled Off), a task's cpu usage will be divided by the total number of CPUs. After issuing this command, you'll be told the new state of this toggle.

*  k  :Kill-a-task
You will be prompted for a PID and then the signal to send.

Entering no PID or a negative number will be interpreted as the default shown in the prompt (the first task displayed). A PID value of zero means the top program itself.

The default signal, as reflected in the prompt, is SIGTERM. However, you can send any signal, via number or name.

If you wish to abort the kill process, do one of the following depending on your progress: 

    1) at the pid prompt, type an invalid number
    2) at the signal prompt, type 0 (or any invalid signal)

   q  :Quit

*  r  :Renice-a-Task
You will be prompted for a PID and then the value to nice it to.

Entering no PID or a negative number will be interpreted as the default shown in the prompt (the first task displayed). A PID value of zero means the top program itself.

A positive nice value will cause a process to lose priority. Conversely, a negative nice value will cause a process to be viewed more favorably by the kernel. As a general rule, ordinary users can only increase the nice value and are prevented from lowering it.

If you wish to abort the renice process, do one of the following depending on your progress: 

    1) at the pid prompt, type an invalid number
    2) at the nice prompt, type <Enter> with no input

   W  :Write-the-Configuration-File
This will save all of your options and toggles plus the current display mode and delay time. By issuing this command just before quitting top, you will be able restart later in exactly that same state.

   X  :Extra-Fixed-Width
Some fields are fixed width and not scalable. As such, they are subject to truncation which would be indicated by a '+' in the last position.

This interactive command can be used to alter the widths of the following fields: 

    field  default    field  default    field  default 
    GID       5       GROUP     8       WCHAN    10
    RUID      5       RUSER     8       nsIPC    10
    SUID      5       SUSER     8       nsMNT    10
    UID       5       USER      8       nsNET    10
                      TTY       8       nsPID    10
                                        nsUSR    10
                                        nsUTS    10

You will be prompted for the amount to be added to the default widths shown above. Entering zero forces a return to those defaults.

If you enter a negative number, top will automatically increase the column size as needed until there is no more truncated data. You can accelerate this process by reducing the delay interval or holding down the <Space> bar.

Note: Whether explicitly or automatically increased, the widths for these fields are never decreased by top. To narrow them you must specify a smaller number or restore the defaults.

   Y  :Inspect-Other-Output
After issuing the 'Y' interactive command, you will be prompted for a target PID. Typing a value or accepting the default results in a separate screen. That screen can be used to view a variety of files or piped command output while the normal top iterative display is paused.

Note: This interactive command is only fully realized when supporting entries have been manually added to the end of the top configuration file. For details on creating those entries, see topic 6c. ADDING INSPECT Entries.

Most of the keys used to navigate the Inspect feature are reflected in its header prologue. There are, however, additional keys available once you have selected a particular file or command. They are familiar to anyone who has used the pager 'less' and are summarized here for future reference. 

    key      function 
    '='      alternate status-line, file or pipeline
    '/'      find, equivalent to 'L' locate
    'n'      find next, equivalent to '&' locate next
    <Space>  scroll down, equivalent to <PgDn>
    'b'      scroll up, equivalent to <PgUp>
    'g'      first line, equivalent to <Home>
    'G'      last line, equivalent to <End>

   Z  :Change-Color-Mapping
This key will take you to a separate screen where you can change the colors for the 'current' window, or for all windows. For details regarding this interactive command see topic 4d. COLOR Mapping.

*
The commands shown with an asterisk ('*') are not available in 'Secure mode', nor will they be shown on the level-1 help screen.

4b. SUMMARY AREA Commands

The summary area interactive commands are always available in both full-screen mode and alternate-display mode. They affect the beginning lines of your display and will determine the position of messages and prompts.

These commands always impact just the 'current' window/field group. See topic 5. ALTERNATE-DISPLAY Provisions and the 'g' interactive command for insight into 'current' windows and field groups.

   C  :Show-scroll-coordinates toggle
Toggle an informational message which is displayed whenever the message line is not otherwise being used. For additional information see topic 5c. SCROLLING a Window.

   l  :Load-Average/Uptime toggle
This is also the line containing the program name (possibly an alias) when operating in full-screen mode or the 'current' window name when operating in alternate-display mode.

   t  :Task/Cpu-States toggle
This command affects from 2 to many summary area lines, depending on the state of the '1', '2' or '3' command toggles and whether or not top is running under true SMP.

This portion of the summary area is also influenced by the 'H' interactive command toggle, as reflected in the total label which shows either 'Tasks' or 'Threads'.

   m  :Memory/Swap-Usage toggle
This command affects the two summary area lines dealing with physical and virtual memory.

   1  :Single/Separate-Cpu-States toggle
This command affects how the 't' command's Cpu States portion is shown. Although this toggle exists primarily to serve massively-parallel SMP machines, it is not restricted to solely SMP environments.

When you see '%Cpu(s):' in the summary area, the '1' toggle is On and all cpu information is gathered in a single line. Otherwise, each cpu is displayed separately as: '%Cpu0, %Cpu1, ...' up to available screen height.

   2  :NUMA-Nodes/Cpu-Summary toggle
This command toggles between the '1' command cpu summary display (only) or a summary display plus the cpu usage statistics for each NUMA Node. It is only available if a system has the requisite NUMA support.

   3  :Expand-NUMA-Node
You will be invited to enter a number representing a NUMA Node. Thereafter, a node summary plus the statistics for each cpu in that node will be shown until either the '1' or '2' command toggle is pressed. This interactive command is only available if a system has the requisite NUMA support.

Note: If the entire summary area has been toggled Off for any window, you would be left with just the message line. In that way, you will have maximized available task rows but (temporarily) sacrificed the program name in full-screen mode or the 'current' window name when in alternate-display mode.

4c. TASK AREA Commands

The task area interactive commands are always available in full-screen mode.

The task area interactive commands are never available in alternate-display mode if the 'current' window's task display has been toggled Off (see topic 5. ALTERNATE-DISPLAY Provisions).

APPEARANCE of task window
   J  :Justify-Numeric-Columns toggle
Alternates between right-justified (the default) and left-justified numeric data. If the numeric data completely fills the available column, this command toggle may impact the column header only.

   j  :Justify-Character-Columns toggle
Alternates between left-justified (the default) and right-justified character data. If the character data completely fills the available column, this command toggle may impact the column header only.

The following commands will also be influenced by the state of the global 'B' (bold enable) toggle.

   b  :Bold/Reverse toggle
This command will impact how the 'x' and 'y' toggles are displayed. Further, it will only be available when at least one of those toggles is On.

   x  :Column-Highlight toggle
Changes highlighting for the current sort field. If you forget which field is being sorted this command can serve as a quick visual reminder, providing the sort field is being displayed. The sort field might not be visible because:
    1) there is insufficient Screen Width 
    2) the 'f' interactive command turned it Off

Note: Whenever 'Searching' and/or 'Other Filtering' is active in a window, column highlighting is temporarily disabled. See the notes at the end of topics 5d. SEARCHING and 5e. FILTERING for an explanation why.

   y  :Row-Highlight toggle
Changes highlighting for "running" tasks. For additional insight into this task state, see topic 3a. DESCRIPTIONS of Fields, the 'S' field (Process Status).

Use of this provision provides important insight into your system's health. The only costs will be a few additional tty escape sequences.

   z  :Color/Monochrome toggle
Switches the 'current' window between your last used color scheme and the older form of black-on-white or white-on-black. This command will alter both the summary area and task area but does not affect the state of the 'x', 'y' or 'b' toggles.

CONTENT of task window

   c  :Command-Line/Program-Name toggle
This command will be honored whether or not the 'COMMAND' column is currently visible. Later, should that field come into view, the change you applied will be seen.

   f | F  :Fields-Management
These keys display a separate screen where you can change which fields are displayed, their order and also designate the sort field. For additional information on these interactive commands see topic 3b. MANAGING Fields.

   o | O  :Other-Filtering
You will be prompted for the selection criteria which then determines which tasks will be shown in the 'current' window. Your criteria can be made case sensitive or case can be ignored. And you determine if top should include or exclude matching tasks.

See topic 5e. FILTERING in a window for details on these and additional related interactive commands.

   S  :Cumulative-Time-Mode toggle
When 'Cumulative mode' is On, each process is listed with the cpu time that it and its dead children have used.

When Off, programs that fork into many separate tasks will appear less demanding. For programs like 'init' or a shell this is appropriate but for others, like compilers, perhaps not. Experiment with two task windows sharing the same sort field but with different 'S' states and see which representation you prefer.

After issuing this command, you'll be informed of the new state of this toggle. If you wish to know in advance whether or not 'Cumulative mode' is in effect, simply ask for help and view the window summary on the second line.

   u | U  :Show-Specific-User-Only
You will be prompted for the uid or name of the user to display. The '-u' option matches on effective user whereas the '-U' option matches on any user (real, effective, saved, or filesystem).

Thereafter, in that task window only matching users will be shown, or possibly no processes will be shown. Prepending an exclamation point ('!') to the user id or name instructs top to display only processes with users not matching the one provided.

Different task windows can be used to filter different users. Later, if you wish to monitor all users again in the 'current' window, re-issue this command but just press <Enter> at the prompt.

   V  :Forest-View-Mode toggle
In this mode, processes are reordered according to their parents and the layout of the COMMAND column resembles that of a tree. In forest view mode it is still possible to toggle between program name and command line (see the 'c' interactive command) or between processes and threads (see the 'H' interactive command).

Note: Typing any key affecting the sort order will exit forest view mode in the 'current' window. See topic 4c. TASK AREA Commands, SORTING for information on those keys.

SIZE of task window

   i  :Idle-Process toggle
Displays all tasks or just active tasks. When this toggle is Off, tasks that have not used any CPU since the last update will not be displayed. However, due to the granularity of the %CPU and TIME+ fields, some processes may still be displayed that appear to have used no CPU.

If this command is applied to the last task display when in alternate-display mode, then it will not affect the window's size, as all prior task displays will have already been painted.

   n | #  :Set-Maximum-Tasks
You will be prompted to enter the number of tasks to display. The lessor of your number and available screen rows will be used.

When used in alternate-display mode, this is the command that gives you precise control over the size of each currently visible task display, except for the very last. It will not affect the last window's size, as all prior task displays will have already been painted.

Note: If you wish to increase the size of the last visible task display when in alternate-display mode, simply decrease the size of the task display(s) above it.

SORTING of task window For compatibility, this top supports most of the former top sort keys. Since this is primarily a service to former top users, these commands do not appear on any help screen. 
   command   sorted-field                  supported 
     A         start time (non-display)      No 
     M         %MEM                          Yes
     N         PID                           Yes
     P         %CPU                          Yes
     T         TIME+                         Yes

Before using any of the following sort provisions, top suggests that you temporarily turn on column highlighting using the 'x' interactive command. That will help ensure that the actual sort environment matches your intent.

The following interactive commands will only be honored when the current sort field is visible. The sort field might not be visible because:
     1) there is insufficient Screen Width 
     2) the 'f' interactive command turned it Off

   <  :Move-Sort-Field-Left
Moves the sort column to the left unless the current sort field is the first field being displayed.

   >  :Move-Sort-Field-Right
Moves the sort column to the right unless the current sort field is the last field being displayed.

The following interactive commands will always be honored whether or not the current sort field is visible.

   f | F  :Fields-Management
These keys display a separate screen where you can change which field is used as the sort column, among other functions. This can be a convenient way to simply verify the current sort field, when running top with column highlighting turned Off.

   R  :Reverse/Normal-Sort-Field toggle
Using this interactive command you can alternate between high-to-low and low-to-high sorts.

Note: Field sorting uses internal values, not those in column display. Thus, the TTY and WCHAN fields will violate strict ASCII collating sequence.

4d. COLOR Mapping

When you issue the 'Z' interactive command, you will be presented with a separate screen. That screen can be used to change the colors in just the 'current' window or in all four windows before returning to the top display.

The following interactive commands are available. 

    4 upper case letters to select a target 
    8 numbers to select a color 
    normal toggles available 
        'B'       :bold disable/enable
        'b'       :running tasks "bold"/reverse
        'z'       :color/mono
    other commands available 
        'a'/'w'   :apply, then go to next/prior
        <Enter>   :apply and exit
        'q'       :abandon current changes and exit

If you use 'a' or 'w' to cycle the targeted window, you will have applied the color scheme that was displayed when you left that window. You can, of course, easily return to any window and reapply different colors or turn colors Off completely with the 'z' toggle.

The Color Mapping screen can also be used to change the 'current' window/field group in either full-screen mode or alternate-display mode. Whatever was targeted when 'q' or <Enter> was pressed will be made current as you return to the top display.

5. ALTERNATE-DISPLAY Provisions

5a. WINDOWS Overview

Field Groups/Windows:
In full-screen mode there is a single window represented by the entire screen. That single window can still be changed to display 1 of 4 different field groups (see the 'g' interactive command, repeated below). Each of the 4 field groups has a unique separately configurable summary area and its own configurable task area.

In alternate-display mode, those 4 underlying field groups can now be made visible simultaneously, or can be turned Off individually at your command.

The summary area will always exist, even if it's only the message line. At any given time only one summary area can be displayed. However, depending on your commands, there could be from zero to four separate task displays currently showing on the screen.

Current Window:
The 'current' window is the window associated with the summary area and the window to which task related commands are always directed. Since in alternate-display mode you can toggle the task display Off, some commands might be restricted for the 'current' window.

A further complication arises when you have toggled the first summary area line Off. With the loss of the window name (the 'l' toggled line), you'll not easily know what window is the 'current' window.

5b. COMMANDS for Windows

   - | _  :Show/Hide-Window(s) toggles
The '-' key turns the 'current' window's task display On and Off. When On, that task area will show a minimum of the columns header you've established with the 'f' interactive command. It will also reflect any other task area options/toggles you've applied yielding zero or more tasks.

The '_' key does the same for all task displays. In other words, it switches between the currently visible task display(s) and any task display(s) you had toggled Off. If all 4 task displays are currently visible, this interactive command will leave the summary area as the only display element.

*  = | +  :Equalize-(reinitialize)-Window(s)
The '=' key forces the 'current' window's task display to be visible. It also reverses any 'i' (idle tasks), 'n' (max tasks), 'u'/'U' (user filter) and 'o'/'O' (other filter) commands that might be active. Also, if the window had been scrolled, it will be reset with this command. See topic 5c. SCROLLING a Window for additional information regarding vertical and horizontal scrolling.

The '+' key does the same for all windows. The four task displays will reappear, evenly balanced. They will also have retained any customizations you had previously applied, except for the 'i' (idle tasks), 'n' (max tasks), 'u'/'U' (user filter), 'o'/'O' (other filter) and scrolling interactive commands.

*  A  :Alternate-Display-Mode toggle
This command will switch between full-screen mode and alternate-display mode.

The first time you issue this command, all four task displays will be shown. Thereafter when you switch modes, you will see only the task display(s) you've chosen to make visible.

*  a | w  :Next-Window-Forward/Backward
This will change the 'current' window, which in turn changes the window to which commands are directed. These keys act in a circular fashion so you can reach any desired 'current' window using either key.

Assuming the window name is visible (you have not toggled 'l' Off), whenever the 'current' window name loses its emphasis/color, that's a reminder the task display is Off and many commands will be restricted.

*  g  :Choose-Another-Window/Field-Group
You will be prompted to enter a number between 1 and 4 designating the field group which should be made the 'current' window.

In full-screen mode, this command is necessary to alter the 'current' window. In alternate-display mode, it is simply a less convenient alternative to the 'a' and 'w' commands.

   G  :Change-Window/Field-Group-Name
You will be prompted for a new name to be applied to the 'current' window. It does not require that the window name be visible (the 'l' toggle to be On).

*
The interactive commands shown with an asterisk ('*') have use beyond alternate-display mode. 
    '=', 'A', 'g'  are always available
    'a', 'w'       act the same with color mapping
                   and fields management

5c. SCROLLING a Window

Typically a task window is a partial view into a systems's total tasks/threads which shows only some of the available fields/columns. With these scrolling keys, you can move that view vertically or horizontally to reveal any desired task or column.

Up,PgUp  :Scroll-Tasks
Move the view up toward the first task row, until the first task is displayed at the top of the 'current' window. The Up arrow key moves a single line while PgUp scrolls the entire window.

Down,PgDn  :Scroll-Tasks
Move the view down toward the last task row, until the last task is the only task displayed at the top of the 'current' window. The Down arrow key moves a single line while PgDn scrolls the entire window.

Left,Right  :Scroll-Columns
Move the view of displayable fields horizontally one column at a time.

Note: As a reminder, some fields/columns are not fixed-width but allocated all remaining screen width when visible. When scrolling right or left, that feature may produce some unexpected results initially.

Additionally, there are special provisions for any variable width field when positioned as the last displayed field. Once that field is reached via the right arrow key, and is thus the only column shown, you can continue scrolling horizontally within such a field. See the 'C' interactive command below for additional information.

Home  :Jump-to-Home-Position
Reposition the display to the un-scrolled coordinates.

End  :Jump-to-End-Position
Reposition the display so that the rightmost column reflects the last displayable field and the bottom task row represents the last task.

Note: From this position it is still possible to scroll down and right using the arrow keys. This is true until a single column and a single task is left as the only display element.

C  :Show-scroll-coordinates toggle
Toggle an informational message which is displayed whenever the message line is not otherwise being used. That message will take one of two forms depending on whether or not a variable width column has also been scrolled. 

  scroll coordinates: y = n/n (tasks), x = n/n (fields)
  scroll coordinates: y = n/n (tasks), x = n/n (fields) + nn

The coordinates shown as n/n are relative to the upper left corner of the 'current' window. The additional '+ nn' represents the displacement into a variable width column when it has been scrolled horizontally. Such displacement occurs in normal 8 character tab stop amounts via the right and left arrow keys.

y = n/n (tasks)
The first n represents the topmost visible task and is controlled by scrolling keys. The second n is updated automatically to reflect total tasks.

x = n/n (fields)
The first n represents the leftmost displayed column and is controlled by scrolling keys. The second n is the total number of displayable fields and is established with the 'f' interactive command.

The above interactive commands are always available in full-screen mode but never available in alternate-display mode if the 'current' window's task display has been toggled Off.

Note: When any form of filtering is active, you can expect some slight aberrations when scrolling since not all tasks will be visible. This is particularly apparent when using the Up/Down arrow keys.

5d. SEARCHING in a Window

You can use these interactive commands to locate a task row containing a particular value.

L  :Locate-a-string
You will be prompted for the case-sensitive string to locate starting from the current window coordinates. There are no restrictions on search string content.

Searches are not limited to values from a single field or column. All of the values displayed in a task row are allowed in a search string. You may include spaces, numbers, symbols and even forest view artwork.

Keying <Enter> with no input will effectively disable the '&' key until a new search string is entered.

&  :Locate-next
Assuming a search string has been established, top will attempt to locate the next occurrence.

When a match is found, the current window is repositioned vertically so the task row containing that string is first. The scroll coordinates message can provide confirmation of such vertical repositioning (see the 'C' interactive command). Horizontal scrolling, however, is never altered via searching.

The availability of a matching string will be influenced by the following factors.

a. Which fields are displayable from the total available,
see topic 3b. MANAGING Fields.
b. Scrolling a window vertically and/or horizontally,
see topic 5c. SCROLLING a Window.
c. The state of the command/command-line toggle,
see the 'c' interactive command.
d. The stability of the chosen sort column,
for example PID is good but %CPU bad.

If a search fails, restoring the 'current' window home (unscrolled) position, scrolling horizontally, displaying command-lines or choosing a more stable sort field could yet produce a successful '&' search.

The above interactive commands are always available in full-screen mode but never available in alternate-display mode if the 'current' window's task display has been toggled Off.

Note: Whenever a search key is typed, top will turn column highlighting Off to prevent false matches on internal non-display escape sequences. Such highlighting will be restored when a window's search string is empty. See the 'x' interactive command for additional information on sort column highlighting.

5e. FILTERING in a Window

You can use the 'Other Filter' feature to establish selection criteria which will then determine which tasks are shown in the 'current' window.

Establishing a filter requires: 1) a field name; 2) an operator; and 3) a selection value, as a minimum. This is the most complex of top's user input requirements so, when you make a mistake, command recall will be your friend. Remember the Up/Down arrow keys or their aliases when prompted for input.

Filter Basics

.
field names are case sensitive and spelled as in the header
.
selection values need not comprise the full displayed field
.
a selection is either case insensitive or sensitive to case
.
the default is inclusion, prepending '!' denotes exclusions
.
multiple selection criteria can be applied to a task window
.
inclusion and exclusion criteria can be used simultaneously
.
the 1 equality and 2 relational filters can be freely mixed
.
separate unique filters are maintained for each task window

If a field is not turned on or is not currently in view, then your selection criteria will not affect the display. Later, should a filtered field become visible, the selection criteria will then be applied.

Keyboard Summary

  o  :Other-Filter (lower case)
You will be prompted to establish a filter that ignores case when matching.

  O  :Other-Filter (upper case)
You will be prompted to establish a case sensitive filter.

 ^O  :Show-Active-Filters (Ctrl key + 'o')
This can serve as a reminder of which filters are active in the 'current' window. A summary will be shown on the message line until you press the <Enter> key.

  =  :Reset-Filtering in current window
This clears all of your selection criteria in the 'current' window. It also has additional impact so please see topic 4a. GLOBAL Commands.

  +  :Reset-Filtering in all windows
This clears the selection criteria in all windows, assuming you are in alternate-display mode. As with the '=' interactive command, it too has additional consequences so you might wish to see topic 5b. COMMANDS for Windows.

Input Requirements

When prompted for selection criteria, the data you provide must take one of two forms. There are 3 required pieces of information, with a 4th as optional. These examples use spaces for clarity but your input generally would not. 

        #1           #2  #3              ( required )
        Field-Name   ?   include-if-value
     !  Field-Name   ?   exclude-if-value
     #4                                  ( optional )

Items #1, #3 and #4 should be self-explanatory. Item #2 represents both a required delimiter and the operator which must be one of either equality ('=') or relation ('<' or '>').

The '=' equality operator requires only a partial match and that can reduce your 'if-value' input requirements. The '>' or '<' relational operators always employ string comparisons, even with numeric fields. They are designed to work with a field's default justification and with homogeneous data. When some field's numeric amounts have been subjected to scaling while others have not, that data is no longer homogeneous.

If you establish a relational filter and you have changed the default 'Numeric' or 'Character' justification, that filter is likely to fail. When a relational filter is applied to a memory field and you have not changed the scaling, it may produce misleading results. This happens, for example, because '100.0m' (MiB) would appear greater than '1.000g' (GiB) when compared as strings.

If your filtered results appear suspect, simply altering justification or scaling may yet achieve the desired objective. See the 'j', 'J' and 'e' interactive commands for additional information.

Potential Problems

These GROUP filters could produce the exact same results or the second one might not display anything at all, just a blank task window. 

     GROUP=root        ( only the same results when )
     GROUP=ROOT        ( invoked via lower case 'o' )

Either of these RES filters might yield inconsistent and/or misleading results, depending on the current memory scaling factor. Or both filters could produce the exact same results. 

     RES>9999          ( only the same results when )
     !RES<10000        ( memory scaling is at 'KiB' )

This nMin filter illustrates a problem unique to scalable fields. This particular field can display a maximum of 4 digits, beyond which values are automatically scaled to KiB or above. So while amounts greater than 9999 exist, they will appear as 2.6m, 197k, etc. 

     nMin>9999         ( always a blank task window )

Potential Solutions

These examples illustrate how 'Other Filtering' can be creatively applied to achieve almost any desired result. Single quotes are sometimes shown to delimit the spaces which are part of a filter or to represent a request for status (^O) accurately. But if you used them with if-values in real life, no matches would be found.

Assuming field nTH is displayed, the first filter will result in only multi-threaded processes being shown. It also reminds us that a trailing space is part of every displayed field. The second filter achieves the exact same results with less typing. 

     !nTH=' 1 '                ( ' for clarity only )
     nTH>1                     ( same with less i/p )

With Forest View mode active and the COMMAND column in view, this filter effectively collapses child processes so that just 3 levels are shown. 

     !COMMAND='       `- '     ( ' for clarity only )

The final two filters appear as in response to the status request key (^O). In reality, each filter would have required separate input. The PR example shows the two concurrent filters necessary to display tasks with priorities of 20 or more, since some might be negative. Then by exploiting trailing spaces, the nMin series of filters could achieve the failed '9999' objective discussed above. 

     'PR>20' + '!PR=-'         ( 2 for right result )
     '!nMin=0 ' + '!nMin=1 ' + '!nMin=2 ' + '!nMin=3 ' ...

Note: When 'Other Filtering' is active, top turns column highlighting Off to prevent false matches on internal non-display escape sequences. Such highlighting will be restored when a window is no longer subject to filtering. See the 'x' interactive command for additional information on sort column highlighting.

6. FILES

6a. SYSTEM Configuration File

The presence of this file will influence which version of the 'help' screen is shown to an ordinary user. More importantly, it will limit what ordinary users are allowed to do when top is running. They will not be able to issue the following commands. 
    k        Kill a task
    r        Renice a task
    d or s   Change delay/sleep interval

The system configuration file is not created by top. Rather, you create this file manually and place it in the /etc directory. Its name must be 'toprc' and must have no leading '.' (period). It must have only two lines.

Here is an example of the contents of /etc/toprc: 

    s        # line 1: 'secure' mode switch
    5.0      # line 2: 'delay'  interval in seconds

6b. PERSONAL Configuration File

This file is written as '$HOME/.your-name-4-top' + 'rc'. Use the 'W' interactive command to create it or update it.

Here is the general layout: 

    global   # line  1: the program name/alias notation
      "      # line  2: id,altscr,irixps,delay,curwin
    per ea   # line  a: winname,fieldscur
    window   # line  b: winflags,sortindx,maxtasks
      "      # line  c: summclr,msgsclr,headclr,taskclr
    global   # line 15: fixed-width incr
      "      # any remaining lines are devoted to the
      "      # generalized 'inspect' provisions
      "      # discussed below

If the $HOME variable is not present, top will try to write the personal configuration file to the current directory, subject to permissions.

6c. ADDING INSPECT Entries

To exploit the 'Y' interactive command, you must add entries at the end of the top personal configuration file. Such entries simply reflect a file to be read or command/pipeline to be executed whose results will then be displayed in a separate scrollable, searchable window.

If you don't know the location or name of your top rcfile, use the 'W' interactive command to rewrite it and note those details.

Inspect entries can be added with a redirected echo or by editing the configuration file. Redirecting an echo risks overwriting the rcfile should it replace (>) rather than append (>>) to that file. Conversely, when using an editor care must be taken not to corrupt existing lines, some of which will contain unprintable data or unusual characters.

Those Inspect entries beginning with a '#' character are ignored, regardless of content. Otherwise they consist of the following 3 elements, each of which must be separated by a tab character (thus 2 '\t' total): 

  .type:  literal 'file' or 'pipe'
  .name:  selection shown on the Inspect screen
  .fmts:  string representing a path or command

The two types of Inspect entries are not interchangeable. Those designated 'file' will be accessed using fopen and must reference a single file in the '.fmts' element. Entries specifying 'pipe' will employ popen, their '.fmts' element could contain many pipelined commands and, none can be interactive.

If the file or pipeline represented in your '.fmts' deals with the specific PID input or accepted when prompted, then the format string must also contain the '%d' specifier, as these examples illustrate. 

  .fmts=  /proc/%d/numa_maps
  .fmts=  lsof -P -p %d

For 'pipe' type entries only, you may also wish to redirect stderr to stdout for a more comprehensive result. Thus the format string becomes: 

  .fmts=  pmap -x %d 2>&1

Here are examples of both types of Inspect entries as they might appear in the rcfile. The first entry will be ignored due to the initial '#' character. For clarity, the pseudo tab depictions (^I) are surrounded by an extra space but the actual tabs would not be. 


  # pipe ^I Sockets ^I lsof -n -P -i 2>&1
  pipe ^I Open Files ^I lsof -P -p %d 2>&1
  file ^I NUMA Info ^I /proc/%d/numa_maps
  pipe ^I Log ^I tail -n100 /var/log/syslog | sort -Mr

Except for the commented entry above, these next examples show what could be echoed to achieve similar results, assuming the rcfile name was '.toprc'. However, due to the embedded tab characters, each of these lines should be preceded by '/bin/echo -e', not just a simple an 'echo', to enable backslash interpretation regardless of which shell you use. 

  "pipe\tOpen Files\tlsof -P -p %d 2>&1" >> ~/.toprc
  "file\tNUMA Info\t/proc/%d/numa_maps" >> ~/.toprc
  "pipe\tLog\ttail -n200 /var/log/syslog | sort -Mr" >> ~/.toprc

Caution: If any inspect entry you create produces output with unprintable characters they will be displayed in either the ^C notation or hexadecimal <FF> form, depending on their value. This applies to tab characters as well, which will show as '^I'. If you want a truer representation, any embedded tabs should be expanded. 

  # next would have contained '\t' ...
  # file ^I <your_name> ^I /proc/%d/status
  # but this will eliminate embedded '\t' ...
  pipe ^I <your_name> ^I cat /proc/%d/status | expand -

The above example takes what could have been a 'file' entry but employs a 'pipe' instead so as to expand the embedded tabs.

Note: While 'pipe' type entries have been discussed in terms of pipelines and commands, there is nothing to prevent you from including shell scripts as well. Perhaps even newly created scripts designed specifically for the 'Y' interactive command.

Lastly, as the number of your Inspect entries grows over time, the 'Options:' row will be truncated when screen width is exceeded. That does not affect operation other than to make some selections invisible.

However, if some choices are lost to truncation but you want to see more options, there is an easy solution hinted at below. 

  Inspection Pause at pid ...
  Use:  left/right then <Enter> ...
  Options:  help  1  2  3  4  5  6  7  8  9  10  11 ...

The entries in the top rcfile would have a number for the '.name' element and the 'help' entry would identify a shell script you've written explaining what those numbered selections actually mean. In that way, many more choices can be made visible.

7. STUPID TRICKS Sampler

Many of these 'tricks' work best when you give top a scheduling boost. So plan on starting him with a nice value of -10, assuming you've got the authority.

7a. Kernel Magic

For these stupid tricks, top needs full-screen mode.

o
The user interface, through prompts and help, intentionally implies that the delay interval is limited to tenths of a second. However, you're free to set any desired delay. If you want to see Linux at his scheduling best, try a delay of .09 seconds or less.

For this experiment, under x-windows open an xterm and maximize it. Then do the following: 

  . provide a scheduling boost and tiny delay via:
      nice -n -10 top -d.09
  . keep sorted column highlighting Off so as to
    minimize path length
  . turn On reverse row highlighting for emphasis
  . try various sort columns (TIME/MEM work well),
    and normal or reverse sorts to bring the most
    active processes into view

What you'll see is a very busy Linux doing what he's always done for you, but there was no program available to illustrate this.

o
Under an xterm using 'white-on-black' colors, on top's Color Mapping screen set the task color to black and be sure that task highlighting is set to bold, not reverse. Then set the delay interval to around .3 seconds.

After bringing the most active processes into view, what you'll see are the ghostly images of just the currently running tasks.

o
Delete the existing rcfile, or create a new symlink. Start this new version then type 'T' (a secret key, see topic 4c. Task Area Commands, SORTING) followed by 'W' and 'q'. Finally, restart the program with -d0 (zero delay).

Your display will be refreshed at three times the rate of the former top, a 300% speed advantage. As top climbs the TIME ladder, be as patient as you can while speculating on whether or not top will ever reach the top.

7b. Bouncing Windows

For these stupid tricks, top needs alternate-display mode.

o
With 3 or 4 task displays visible, pick any window other than the last and turn idle processes Off using the 'i' command toggle. Depending on where you applied 'i', sometimes several task displays are bouncing and sometimes it's like an accordion, as top tries his best to allocate space.

o
Set each window's summary lines differently: one with no memory ('m'); another with no states ('t'); maybe one with nothing at all, just the message line. Then hold down 'a' or 'w' and watch a variation on bouncing windows  --  hopping windows.

o
Display all 4 windows and for each, in turn, set idle processes to Off using the 'i' command toggle. You've just entered the "extreme bounce" zone.

7c. The Big Bird Window

This stupid trick also requires alternate-display mode.

o
Display all 4 windows and make sure that 1:Def is the 'current' window. Then, keep increasing window size with the 'n' interactive command until all the other task displays are "pushed out of the nest".

When they've all been displaced, toggle between all visible/invisible windows using the '_' command toggle. Then ponder this:

   is top fibbing or telling honestly your imposed truth?

7d. The Ol' Switcheroo

This stupid trick works best without alternate-display mode, since justification is active on a per window basis.

o
Start top and make COMMAND the last (rightmost) column displayed. If necessary, use the 'c' command toggle to display command lines and ensure that forest view mode is active with the 'V' command toggle.

Then use the up/down arrow keys to position the display so that some truncated command lines are shown ('+' in last position). You may have to resize your xterm to produce truncation.

Lastly, use the 'j' command toggle to make the COMMAND column right justified.

Now use the right arrow key to reach the COMMAND column. Continuing with the right arrow key, watch closely the direction of travel for the command lines being shown.



   some lines travel left, while others travel right


   eventually all lines will Switcheroo, and move right

8. BUGS

To report bugs, follow the instructions at:
    http://www.debian.org/Bugs/Reporting

9. HISTORY Former top

The original top was written by Roger Binns, based on Branko Lankester's <lankeste@fwi.uva.nl> ps program.

Robert Nation <nation@rocket.sanders.lockheed.com> adapted it for the proc file system.

Helmut Geyer <Helmut.Geyer@iwr.uni-heidelberg.de> added support for configurable fields.

Plus many other individuals contributed over the years.

10. AUTHOR

This entirely new and enhanced replacement was written by:
    Jim Warner, <james.warner@comcast.net>

With invaluable help from:
    Craig Small, <csmall@enc.com.au>
    Albert Cahalan, <albert@users.sf.net>


 

11. SEE Also

free(1), ps(1), uptime(1), atop(1), slabtop(1), vmstat(8), w(1).