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htop - Online in the Cloud

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htop - interactive process viewer


htop [-dChusv]


Htop is a free (GPL) ncurses-based process viewer for Linux.

It is similar to top, but allows you to scroll vertically and horizontally, so you can see
all the processes running on the system, along with their full command lines, as well as
viewing them as a process tree, selecting multiple processes and acting on them all at

Tasks related to processes (killing, renicing) can be done without entering their PIDs.


Mandatory arguments to long options are mandatory for short options too.

-d --delay=DELAY
Delay between updates, in tenths of seconds

-C --no-color --no-colour
Start htop in monochrome mode

-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)

-u --user=USERNAME
Show only the processes of a given user

-v --version
Output version information and exit


The following commands are supported while in htop:

Arrows, PgUP, PgDn, Home, End
Scroll the process list.

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.

U Untag all processes (remove all tags added with the Space key).

s Trace process system calls: if strace(1) is installed, pressing this key will attach
it to the currently selected process, presenting 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.

F1, h, ?
Go to the help screen

F2, S
Go to the setup screen, where you can configure the meters displayed 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.

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.

F5, t
Tree view: organize processes by parenthood, and layout the relations 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 On sorted view, select a field for sorting, also accessible through < and >. The
current sort field is indicated by a highlight in the header. On tree view, expand
or collapse the current subtree. A "+" indicator in the tree node indicates that it
is collapsed.

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)

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

I Invert the sort order: if sort order is increasing, switch to decreasing, and vice-

+, - When in tree view mode, expand or collapse subtree. When a subtree is collapsed a "+"
sign shows to the left of the process name.

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.

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.)

p Show full paths to running programs, where applicable. (This is a toggle key.)

Refresh: redraw screen and recalculate values.

PID search: type in process ID and the selection highlight will be moved to it.


The following columns can display data about each process. A value of '-' in all the rows
indicates that a column is unsupported on your system, or currently unimplemented in htop.
The names below are the ones used in the "Available Columns" section of the setup screen.
If a different name is shown in htop's main screen, it is shown below in parenthesis.

The full command line of the process (i.e. program name and arguments).

PID The process ID.

The state of the process:
S for sleeping (idle)
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.

The process's session ID.

The controlling terminal of the process.

The process ID of the foreground process group of the controlling terminal.

The number of page faults happening in the main memory.

The number of minor faults for the process's waited-for children (see MINFLT above).

The number of page faults happening out of the main memory.

The number of major faults for the process's waited-for children (see MAJFLT above).

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.

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.

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).

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

The kernel's internal priority for the process, usually just its nice value plus
twenty. Different for real-time processes.

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 restrictions for adjusting priority apply.

The time the process was started.

The ID of the CPU the process last executed on.

The size of the virtual memory of the process.

The resident set size (text + data + stack) of the process (i.e. the size of the
process's used physical memory).

The size of the process's shared pages.

The text resident set size of the process (i.e. the size of the process's executable

The data resident set size (data + stack) of the process (i.e. the size of anything
except the process's executable instructions).

The library size of the process.

The size of the dirty pages of the process.

The user ID of the process owner.

The percentage of the CPU time that the process is currently using.

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.

The time, measured in clock ticks that the process has spent in user and system time
(see UTIME, STIME above).

NLWP The number of 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.

The number of bytes the process has read.

The number of bytes the process has written.

The number of read(2) syscalls for the process.

The number of write(2) syscalls for the process.

Bytes of read(2) I/O for the process.

Bytes of write(2) I/O for the process.

Bytes of cancelled write(2) I/O.

The I/O rate of read(2) in bytes per second, for the process.

The I/O rate of write(2) in bytes per second, for the process.

The I/O rate, IO_READ_RATE + IO_WRITE_RATE (see above).

Which cgroup the process is in.

OOM OOM killer score.

The I/O scheduling class followed by the priority if the class supports it:
R for Realtime
B for Best-effort
id for Idle

All other flags
Currently unsupported (always displays '-').


By default htop reads its configuration from the XDG-compliant path ~/.config/htop/htoprc
-- the configuration file is overwritten 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

You may override the location of the configuration file using the $HTOPRC environment
variable (so you can have multiple configurations for different machines that share the
same home directory, for example).


Memory sizes in htop are displayed as they are in tools from the GNU Coreutils (when ran
with the --human-readable option). This means that sizes are printed in powers of 1024.
(e.g., 1023M = 1072693248 Bytes)

The decision to use this convention was made in order to conserve screen space and make
memory size representations consistent throughout htop.

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