HTOP(1) User Commands HTOP(1)
NAME
htop, pcp-htop - interactive process viewer
SYNOPSIS
htop [-dCFhpustvH]
pcp-htop [-dCFhpustvH] [--host/-h host]
DESCRIPTION
htop is a cross-platform ncurses-based process viewer.
It is similar to top, but allows you to scroll vertically and horizon-
tally, and interact using a pointing device (mouse). You can observe
all processes running on the system, along with their command line argu-
ments, as well as view them in a tree format, select multiple processes
and act on them all at once.
Tasks related to processes (killing, renicing) can be done without en-
tering their PIDs.
pcp-htop is a version of htop built using the Performance Co-Pilot (PCP)
Metrics API (see PCPIntro(1), PMAPI(3)), allowing to extend htop to dis-
play values from arbitrary metrics. See the section below titled CONFIG
FILES for further details.
COMMAND-LINE OPTIONS
Mandatory arguments to long options are mandatory for short options too.
-d --delay=DELAY
Delay between updates, in tenths of a second. If the delay value
is less than 1, it is increased to 1, i.e. 1/10 second. If the
delay value is greater than 100, it is decreased to 100, i.e. 10
seconds.
-C --no-color --no-colour
Start htop in monochrome mode
-F --filter=FILTER
Filter processes by terms matching the commands. The terms are
matched case-insensitive and as fixed strings (not regexs). You
can separate multiple terms with "|".
-h --help
Display a help message and exit
-p --pid=PID,PID...
Show only the given PIDs
-s --sort-key COLUMN
Sort by this column (use --sort-key help for a column list).
This will force a list view unless you specify -t at the same
time. Sorting in tree mode applies to the direct children of
each process.
-u --user[=USERNAME|UID]
Show only the processes of a given user, or self if omitted
-U --no-unicode
Do not use unicode but ASCII characters for graph meters
-M --no-mouse
Disable support of mouse control
--readonly
Disable all system and process changing features
-V --version
Output version information and exit
-t --tree
Show processes in tree view. This can be used to force a tree
view when requesting a sort order with -s.
-H --highlight-changes=DELAY
Highlight new and old processes
--drop-capabilities[=off|basic|strict]
Linux only; this option needs to have been enabled at compile-
time and requires libcap support at runtime.
Drop unneeded Linux capabilities. In strict mode features like
killing, changing process priorities and reading process delay
accounting information will not work due to fewer capabilities
being held.
INTERACTIVE COMMANDS
The following commands are supported while in htop:
Tab, Shift-Tab
Select the next / the previous screen tab to display. You can en-
able showing the screen tab names in the Setup screen (F2).
Up, Alt-k
Select (highlight) the previous process in the process list. Scroll
the list if necessary.
Down, Alt-j
Select (highlight) the next process in the process list. Scroll the
list if necessary.
Left, Alt-h
Scroll the process list left.
Right, Alt-l
Scroll the process list right.
PgUp, PgDn
Scroll the process list up or down one window.
Home Scroll to the top of the process list and select the first process.
End Scroll to the bottom of the process list and select the last
process.
Ctrl-A, ^
Scroll left to the beginning of the process entry (i.e. beginning
of line).
Ctrl-E, $
Scroll right to the end of the process entry (i.e. end of line).
Space
Tag or untag a process. Commands that can operate on multiple
processes, like "kill", will then apply over the list of tagged
processes, instead of the currently highlighted one.
c Tag the current process and its children. Commands that can operate
on multiple processes, like "kill", will then apply over the list
of tagged processes, instead of the currently highlighted one.
U Untag all processes (remove all tags added with the Space or c
keys).
s Trace process system calls: if strace(1) is installed, pressing
this key will attach it to the currently selected process, present-
ing a live update of system calls issued by the process.
l Display open files for a process: if lsof(1) is installed, pressing
this key will display the list of file descriptors opened by the
process.
w Display the command line of the selected process in a separate
screen, wrapped onto multiple lines as needed.
x Display the active file locks of the selected process in a separate
screen.
F1, h, ?
Go to the help screen
F2, S
Go to the setup screen, where you can configure the meters dis-
played at the top of the screen, set various display options,
choose among color schemes, and select which columns are displayed,
in which order.
F3, /
Incrementally search the command lines of all the displayed
processes. The currently selected (highlighted) command will update
as you type. While in search mode, pressing F3 will cycle through
matching occurrences. Pressing Shift-F3 will cycle backwards.
Alternatively the search can be started by simply typing the com-
mand you are looking for, although for the first character normal
key bindings take precedence.
F4, \
Incremental process filtering: type in part of a process command
line and only processes whose names match will be shown. To cancel
filtering, enter the Filter option again and press Esc. The match-
ing is done case-insensitive. Terms are fixed strings (no regex).
You can separate multiple terms with "|".
F5, t
Tree view: organize processes by parenthood, and layout the rela-
tions between them as a tree. Toggling the key will switch between
tree and your previously selected sort view. Selecting a sort view
will exit tree view.
F6, <, >
Selects a field for sorting, also accessible through < and >. The
current sort field is indicated by a highlight in the header.
F7, ]
Increase the selected process's priority (subtract from 'nice'
value). This can only be done by the superuser.
F8, [
Decrease the selected process's priority (add to 'nice' value)
Shift-F7, }
Increase the selected process's autogroup priority (subtract from
autogroup 'nice' value). This can only be done by the superuser.
Shift-F8, {
Decrease the selected process's autogroup priority (add to auto-
group 'nice' value)
F9, k
"Kill" process: sends a signal which is selected in a menu, to one
or a group of processes. If processes were tagged, sends the signal
to all tagged processes. If none is tagged, sends to the currently
selected process.
F10, q
Quit
I Invert the sort order: if sort order is increasing, switch to de-
creasing, and vice-versa.
+, -, *
When in tree view mode, expand or collapse subtree. When a subtree
is collapsed a "+" sign shows to the left of the process name.
Pressing "*" will expand or collapse all children of PIDs without
parents, so typically PID 1 (init) and PID 2 (kthreadd on Linux, if
kernel threads are shown).
a (on multiprocessor machines)
Set CPU affinity: mark which CPUs a process is allowed to use.
u Show only processes owned by a specified user.
N Sort by PID.
M Sort by memory usage (top compatibility key).
P Sort by processor usage (top compatibility key).
T Sort by time (top compatibility key).
F "Follow" process: if the sort order causes the currently selected
process to move in the list, make the selection bar follow it. This
is useful for monitoring a process: this way, you can keep a
process always visible on screen. When a movement key is used,
"follow" loses effect.
K Hide kernel threads: prevent the threads belonging the kernel to be
displayed in the process list. (This is a toggle key.)
H Hide user threads: on systems that represent them differently than
ordinary processes (such as recent NPTL-based systems), this can
hide threads from userspace processes in the process list. (This is
a toggle key.)
O Hide containerized processes: prevent processes running in a con-
tainer from being displayed in the process list. (This is a toggle
key.)
p Show full paths to running programs, where applicable. (This is a
toggle key.)
Z Pause/resume process updates.
m Merge exe, comm and cmdline, where applicable. (This is a toggle
key.)
Ctrl-L
Refresh: redraw screen and recalculate values.
Numbers
PID search: type in process ID and the selection highlight will be
moved to it.
COLUMNS
The following columns can display data about each process. A value of
'-' in all the rows indicates that a column is unsupported on your sys-
tem, or currently unimplemented in htop. The names below are the ones
used in the "Available Columns" section of the setup screen. If a dif-
ferent name is shown in htop's main screen, it is shown below in paren-
thesis.
Command
The full command line of the process (i.e. program name and argu-
ments).
If the option 'Merge exe, comm and cmdline in Command' (toggled by
the 'm' key) is active, the executable path (/proc/[pid]/exe) and
the command name (/proc/[pid]/comm) are also shown merged with the
command line, if available.
The program basename is highlighted if set in the configuration.
Additional highlighting can be configured for stale executables
(cf. EXE column below).
The Command column should be the last column in each screen as can
get very long and profits from being able to extend its length dy-
namically.
COMM The command name of the process obtained from /proc/[pid]/comm, if
readable.
Requires Linux kernel 2.6.33 or newer.
EXE The abbreviated basename of the executable of the process, obtained
from /proc/[pid]/exe, if readable. htop is able to read this file
on linux for ALL the processes only if it has the capability
CAP_SYS_PTRACE or root privileges.
The basename is marked in red if the executable used to run the
process has been replaced or deleted on disk since the process
started. The information is obtained by processing the contents of
/proc/[pid]/exe.
Furthermore the basename is marked in yellow if any library is re-
ported as having been replaced or deleted on disk since it was last
loaded. The information is obtained by processing the contents of
/proc/[pid]/maps.
When deciding the color the replacement of the main executable al-
ways takes precedence over replacement of any other library. If
only the memory map indicates a replacement of the main executable,
this will show as if any other library had been replaced or
deleted.
This additional color markup can be configured in the "Display Op-
tions" section of the setup screen.
Displaying EXE requires CAP_SYS_PTRACE and PTRACE_MODE_READ_FSCRED.
PID The process ID.
STATE (S)
The state of the process:
S for sleeping
I for idle (longer inactivity than sleeping on platforms that
distinguish)
R for running
D for disk sleep (uninterruptible)
Z for zombie (waiting for parent to read its exit status)
T for traced or suspended (e.g by SIGTSTP)
W for paging
PPID The parent process ID.
PGRP The process's group ID.
SESSION (SID)
The process's session ID.
TTY The controlling terminal of the process.
TPGID
The process ID of the foreground process group of the controlling
terminal.
MINFLT
The number of page faults happening in the main memory.
CMINFLT
The number of minor faults for the process's waited-for children
(see MINFLT above).
MAJFLT
The number of page faults happening out of the main memory.
CMAJFLT
The number of major faults for the process's waited-for children
(see MAJFLT above).
UTIME (UTIME+)
The user CPU time, which is the amount of time the process has
spent executing on the CPU in user mode (i.e. everything but system
calls), measured in clock ticks.
STIME (STIME+)
The system CPU time, which is the amount of time the kernel has
spent executing system calls on behalf of the process, measured in
clock ticks.
CUTIME (CUTIME+)
The children's user CPU time, which is the amount of time the
process's waited-for children have spent executing in user mode
(see UTIME above).
CSTIME (CSTIME+)
The children's system CPU time, which is the amount of time the
kernel has spent executing system calls on behalf of all the
process's waited-for children (see STIME above).
PRIORITY (PRI)
The kernel's internal priority for the process, usually just its
nice value plus twenty. Different for real-time processes.
NICE (NI)
The nice value of a process, from 19 (low priority) to -20 (high
priority). A high value means the process is being nice, letting
others have a higher relative priority. The usual OS permission re-
strictions for adjusting priority apply.
STARTTIME (START)
The time the process was started.
PROCESSOR (CPU)
The ID of the CPU the process last executed on.
M_VIRT (VIRT)
The size of the virtual memory of the process.
M_RESIDENT (RES)
The resident set size (text + data + stack) of the process (i.e.
the size of the process's used physical memory).
M_SHARE (SHR)
The size of the process's shared pages.
M_TRS (CODE)
The text resident set size of the process (i.e. the size of the
process's executable instructions).
M_DRS (DATA)
The data resident set size (data + stack) of the process (i.e. the
size of anything except the process's executable instructions).
M_LRS (LIB)
The library size of the process.
M_SWAP (SWAP)
The size of the process's swapped pages.
M_PSS (PSS)
The proportional set size, same as M_RESIDENT but each page is di-
vided by the number of processes sharing it.
M_M_PSSWP (PSSWP)
The proportional swap share of this mapping, unlike M_SWAP this
does not take into account swapped out page of underlying shmem ob-
jects.
ST_UID (UID)
The user ID of the process owner.
PERCENT_CPU (CPU%)
The percentage of the CPU time that the process is currently using.
This is the default way to represent CPU usage in Linux. Each
process can consume up to 100% which means the full capacity of the
core it is running on. This is sometimes called "Irix mode" e.g. in
top(1).
PERCENT_NORM_CPU (NCPU%)
The percentage of the CPU time that the process is currently using
normalized by CPU count. This is sometimes called "Solaris mode"
e.g. in top(1).
PERCENT_MEM (MEM%)
The percentage of memory the process is currently using (based on
the process's resident memory size, see M_RESIDENT above).
USER The username of the process owner, or the user ID if the name can't
be determined.
On Linux the username is highlighted if the process has elevated
privileges, i.e. if it has been started from binaries with file ca-
pabilities set or retained Linux capabilities, via the ambient set,
after switching from the root user.
TIME (TIME+)
The time, measured in clock ticks that the process has spent in
user and system time (see UTIME, STIME above).
NLWP The number of Light-Weight Processes (=threads) in the process.
TGID The thread group ID.
CTID OpenVZ container ID, a.k.a virtual environment ID.
VPID OpenVZ process ID.
VXID VServer process ID.
RCHAR (RD_CHAR)
The number of bytes the process has read.
WCHAR (WR_CHAR)
The number of bytes the process has written.
SYSCR (RD_SYSC)
The number of read(2) syscalls for the process.
SYSCW (WR_SYSC)
The number of write(2) syscalls for the process.
RBYTES (IO_RBYTES)
Bytes of read(2) I/O for the process.
WBYTES (IO_WBYTES)
Bytes of write(2) I/O for the process.
CNCLWB (IO_CANCEL)
Bytes of cancelled write(2) I/O.
IO_READ_RATE (DISK READ)
The I/O rate of read(2) in bytes per second, for the process.
IO_WRITE_RATE (DISK WRITE)
The I/O rate of write(2) in bytes per second, for the process.
IO_RATE (DISK R/W)
The I/O rate, IO_READ_RATE + IO_WRITE_RATE (see above).
CGROUP
Which cgroup the process is in. For a shortened view see the CC-
GROUP column below.
CCGROUP
Shortened view of the cgroup name that the process is in. This
performs some pattern-based replacements to shorten the displayed
string and thus condense the information.
/*.slice is shortened to /[*] (exceptions below)
/system.slice is shortened to /[S]
/user.slice is shortened to /[U]
/user-*.slice is shortened to /[U:*] (directly preceding /[U]
before dropped)
/machine.slice is shortened to /[M]
/machine-*.scope is shortened to /[SNC:*] (SNC: systemd nspawn
container), uppercase for the monitor
/lxc.monitor.* is shortened to /[LXC:*]
/lxc.payload.* is shortened to /[lxc:*]
/*.scope is shortened to /!*
/*.service is shortened to /* (suffix removed)
Encountered escape sequences (e.g. from systemd) inside the cgroup
name are not decoded.
OOM OOM killer score.
CTXT Incremental sum of voluntary and nonvoluntary context switches.
IO_PRIORITY (IO)
The I/O scheduling class followed by the priority if the class sup-
ports it:
R for Realtime
B for Best-effort
id for Idle
PERCENT_CPU_DELAY (CPUD%)
The percentage of time spent waiting for a CPU (while runnable).
Requires CAP_NET_ADMIN.
PERCENT_IO_DELAY (IOD%)
The percentage of time spent waiting for the completion of synchro-
nous block I/O. Requires CAP_NET_ADMIN.
PERCENT_SWAP_DELAY (SWAPD%)
The percentage of time spent swapping in pages. Requires
CAP_NET_ADMIN.
AGRP The autogroup identifier for the process. Requires Linux CFS to be
enabled.
ANI The autogroup nice value for the process autogroup. Requires Linux
CFS to be enabled.
All other flags
Currently unsupported (always displays '-').
EXTERNAL LIBRARIES
While htop depends on most of the libraries it uses at build time there
are two noteworthy exceptions to this rule. These exceptions both relate
to data displayed in meters displayed in the header of htop and were in-
tentionally created as optional runtime dependencies instead. These ex-
ceptions are described below:
libsystemd
The bindings for libsystemd are used in the SystemD meter to de-
termine the number of active services and the overall system
state. Looking for the functions to determine these information
at runtime allows for builds to support these meters without
forcing the package manager to install these libraries on systems
that otherwise don't use systemd.
Summary: no build time dependency, optional runtime dependency on
libsystemd via dynamic loading, with systemctl(1) fallback.
libsensors
The bindings for libsensors are used for the CPU temperature
readings in the CPU usage meters if displaying the temperature is
enabled through the setup screen. In order for htop to show these
temperatures correctly though, a proper configuration of libsen-
sors through its usual configuration files is assumed and that
all CPU cores correspond to temperature sensors from the coretemp
driver with core 0 corresponding to a sensor labelled "Core 0".
The package temperature may be given as "Package id 0". If miss-
ing it is inferred as the maximum value from the available per-
core readings.
Summary: build time dependency on libsensors(3) C header files,
optional runtime dependency on libsensors(3) via dynamic loading.
CONFIG FILES
By default htop reads its configuration from the XDG-compliant path
~/.config/htop/htoprc. The configuration file is overwritten upon clean
exit by htop's in-program Setup configuration, so it should not be hand-
edited. If no user configuration exists htop tries to read the system-
wide configuration from /etc/htoprc and as a last resort, falls back to
its hard coded defaults.
You may override the location of the configuration file using the $HTO-
PRC environment variable (so you can have multiple configurations for
different machines that share the same home directory, for example).
The pcp-htop utility makes use of htoprc in a similar way. However,
pcp-htop reads its configuration from a path more conventionally used by
Performance Co-Pilot tools, ~/.pcp/htop/htoprc, in order to provide sep-
arate configuration when both htop and pcp-htop are installed and in
use. pcp-htop supports additional configuration files below the same
directory allowing new meters, columns and screen tabs to be added via
the Setup screen (F2). This displays additional Available Meters,
Available Column and Screen Tabs for each meter, column or screen con-
figuration file.
These pcp-htop configuration files are read once at startup. The format
of these files is described in detail in the pcp-htop(5) manual page.
This functionality makes available many thousands of Performance Co-Pi-
lot metrics for display by pcp-htop, as well as the ability to display
custom metrics added at individual sites. Applications and services in-
strumented using the OpenMetrics format https://openmetrics.io can also
be displayed by pcp-htop if the pmdaopenmetrics(1) component is config-
ured.
The configuration for both htop and pcp-htop is only saved when a clean
exit is performed. Sending any signal will cause all configuration
changes to be lost.
MEMORY SIZES
Memory sizes in htop are displayed in a human-readable form. Sizes are
printed in powers of 1024 using binary IEC units. If no suffix is shown
the units are implicitly K as in KiB (kibibyte, 1 KiB = 1024 bytes).
The decision to use this convention was made in order to conserve screen
space and make memory size representations consistent throughout htop as
allocations are granular to full memory pages (4 KiB for most plat-
forms).
SEE ALSO
proc(5), top(1), free(1), ps(1), uptime(1) and limits.conf(5).
SEE ALSO FOR PCP
pmdaopenmetrics(1), PCPIntro(1), PMAPI(3), and pcp-htop(5).
AUTHORS
htop was originally developed by Hisham Muhammad. Nowadays it is main-
tained by the community at <htop@groups.io>.
pcp-htop is maintained as a collaboration between the <htop@groups.io>
and <pcp@groups.io> communities, and forms part of the Performance Co-
Pilot suite of tools.
COPYRIGHT
Copyright © 2004-2019 Hisham Muhammad.
Copyright © 2020-2025 htop dev team.
License GPLv2+: GNU General Public License version 2 or, at your option,
any later version.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
htop 3.4.1 2025 HTOP(1)
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