top

Real-time system process monitor

TLDR

Start top

$ top

Do not show any idle or zombie processes

$ top -i

Show only processes owned by a specific user

$ top -u [username]

Sort processes by a field

$ top -o %MEM

Show individual threads of a process

$ top -Hp [process_id]

Monitor specific PIDs

$ top -p [1234],[5678]

Run in batch mode for scripting (single snapshot)

$ top -b -n 1

Set update interval to 5 seconds

$ top -d 5

Show full command lines instead of program names

$ top -c

SYNOPSIS

top [-b] [-c] [-d delay] [-H] [-i] [-n iterations] [-o field] [-p pid] [-S] [-u user] [-w width]

top provides a dynamic real-time view of a running system. It displays system summary information and a list of processes or threads currently being managed by the Linux kernel. The display is updated periodically and can be customized interactively.

PARAMETERS

-b, --batch

Run in batch mode (non-interactive), useful for piping output.

-c, --cmdline-toggle

Toggle between command line and program name display.

-d SECS, --delay=SECS

Set the delay between screen updates (default: 3.0 seconds).

-e, --scale-task-mem

Scale task memory values (k/m/g/t/p).

-E, --scale-summary-mem

Scale summary memory values (k/m/g/t/p/e).

-H, --threads-show

Display individual threads instead of processes.

-i, --idle-toggle

Hide idle and zombie processes.

-n NUMBER, --iterations=NUMBER

Set maximum number of iterations before exit.

-o FIELD, --sort-override=FIELD

Override the default sort field. Prefix with + or - for ascending/descending.

-p PIDLIST, --pid=PIDLIST

Monitor only specified process IDs (comma-separated).

-S, --accum-time-toggle

Toggle cumulative time mode, showing CPU time used by each process and its dead children.

-s, --secure-mode

Start top in secure mode, disabling potentially dangerous interactive commands.

-u USER, --filter-only-euser=USER

Show only processes for specified effective user.

-U USER, --filter-any-user=USER

Show processes for specified user (real, effective, saved, filesystem).

-w WIDTH, --width=WIDTH

Override screen width in batch mode (minimum 80 characters).

INTERACTIVE COMMANDS

h or ?: Display help screenq: Quit topd or s: Change delay between updatesk: Kill a process (prompts for PID and signal)r: Renice a process (prompts for PID and nice value)f: Manage displayed fieldso: Add filter expressionc: Toggle command line/program nameV: Toggle forest view mode1: Toggle single/separate CPU statesm: Cycle memory display modest: Cycle CPU states display modesR: Reverse sort orderP: Sort by CPU usageM: Sort by memory usageT: Sort by cumulative time< or >: Move sort column left/rightW: Write configuration file

PROCESS STATUS CODES

D: Uninterruptible sleepI: Idle kernel threadR: RunningS: Sleeping (interruptible)T: Stopped by job control signalt: Stopped by debuggerZ: Zombie

INSTALL

sudo apt install procps

sudo dnf install procps-ng

sudo pacman -S procps-ng

sudo apk add procps-ng

sudo zypper install procps

brew install procps

nix profile install nixpkgs#procps

CAVEATS

The configuration file is saved to ~/.config/procps/toprc. Running in batch mode (-b) is recommended for scripting as it disables interactive features and produces parseable output. The default delay between updates is 3.0 seconds.

HISTORY

top was originally written by Roger Binns and has been part of the procps (now procps-ng) package. It has been a standard system monitoring tool on Unix-like systems since the 1980s.

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