Interactive Process viewer, find the CPU-intensive programs currently running.

      htop options

       -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 
       -u --user=USERNAME        Show only the processes of a given user 
       -p                        Start working thread for pagemap memory stats
       -s --sort-key COLUMN      Sort by this column (use --sort-key help for a column list) 
       -v --version              Output version information and exit 

Interactive commands:

   Arrows, PgUP, PgDn, Home, End
               Scroll the process list. 
   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. 
   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, <, >    Select a field for sorting. 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) 
   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 decreasing, 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.
   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.)
   Ctrl-L      Refresh: redraw screen and recalculate values. 
   Numbers     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 parentheses.

Command    The full command line of the process (i.e program name and arguments). 
PID        The process ID.
PPID       The parent process ID.
PGRP       The process’s group ID.
SESSION (SESN)    The process’s session ID. 
TTY_NR (TTY)      The controlling terminal of the process. 
TPGID             The process ID of the foreground process group of the controlling terminal. 
STATE (S)         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 
PROCESSOR (CPU)   The ID of the CPU the process last executed on. 
NLWP              The number of threads in the process.
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. Only root can lower the value. 
PERCENT_CPU (CPU%) The percentage of the CPU time that the process is currently using. 
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. 
TIME (TIME+)      The time, measured in clock ticks that the process has spent in user and system
                  time (see UTIME, STIME above). 
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            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 kernels internal priority for the process, usually just its nice value plus
                  twenty. Different for real-time processes. 
PERCENT_MEM       The percentage of memory the process is currently using (based on the process’s
                  resident memory size, see M_RESIDENT below). 
M_SIZE (VIRT)     Size in memory of the total program size. 
M_RESIDENT (RES)  The resident set size, i.e the size of the text and data sections, plus stack usage. 
M_SHARE (SHR)     The size of the process’s shared pages 
M_TRS (CODE)      The size of the text segment of the process (i.e the size of the processes
                  executable instructions). 
M_LRS (LIB)       The library size of the process. 
M_DRS (DATA)      The size of the data segment plus stack usage of the process. 
M_DT (DIRTY)      The size of the dirty pages of the process. 
ST_UID (UID)      The user ID of the process owner. 
USER              The username of the process owner, or the user ID if the name can’t be determined.
STARTTIME         The time the process was started. 
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. 
IO_READ_RATE (IORR) The I/O rate of read(2) in bytes per second, for the process. 
IO_WRITE_RATE (IOWR) The I/O rate of write(2) in bytes per second, for the process. 
IO_RATE (IO)      The I/O rate, IO_READ_RATE + IO_WRITE_RATE (see above). 
CNCLWB (IO_CANCEL) Bytes of cancelled write(2) I/O. 
CGROUP            Which cgroup the process is in. 
CTID              OpenVZ container ID, a.k.a virtual environment ID.
VPID              OpenVZ process ID.
VXID              VServer process ID.
All other flags   Currently unsupported (always displays '-'). 

htop displays per-process CPU usage (not total server load) it is useful for seeing how much work the machine is doing now compared to some point in the past.


To display processes sorted by USER, updating every 5 seconds:

$ htop -s USER --delay=50

“Venice is like eating an entire box of chocolate liqueurs at one go” ~ Truman Capote

Related Linux commands

htop - htop home page.
Explanation of everything you can see in htop/top on Linux - Pēteris Ņikiforovs.
kill - Stop a process from running.
top - List processes running on the system.
Equivalent Windows command: TaskList - Display all running applications and services.

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