Linux and UNIX Man Pages

Test Your Knowledge in Computers #95
Difficulty: Easy
SMH is an Internet expression that stands for 'shake my head' or 'shaking my head'.
True or False?
Linux & Unix Commands - Search Man Pages

htop(1) [debian man page]

HTOP(1) 							       Utils								   HTOP(1)

htop - interactive process viewer SYNOPSIS
htop [-dChusv] DESCRIPTION
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. Tasks related to processes (killing, renicing) can be done without entering their PIDs. COMMAND-LINE OPTIONS Mandatory arguments to long options are madatory 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 -u --user=USERNAME Show only the processes of a given user -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
The following commands are supported while in htop: 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 pro- cesses, 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. L Trace process library calls: if ltrace(1) is installed, pressing this key will attach it to the currently selected process, presenting a live update of library calls issued 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. 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 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. 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 it's 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 oth- ers 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 it's 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 '-'). SEE ALSO
proc(5), top(1), free(1), ps(1), uptime(1) AUTHORS
htop is developed by Hisham Muhammad <>. This man page was written by Bartosz Fenski <> for the Debian GNU/Linux distribution (but it may be used by others). It was updated by Hisham Muhammad, and later by Vincent Launchbury, who wrote the 'Columns' section. htop 1.0.1 2011 HTOP(1)

Featured Tech Videos