htop is an interactive process viewer for Unix systems, similar to the top command but with an improved user interface and more features. It allows users to monitor system processes and their resource usage in real-time. Here's a detailed explanation of htop, including how to use it and what features it provides:
Usage of htop
Basic Usage
To use htop, open a terminal and simply type:
htop
By default, htop displays an interactive process list with various columns showing detailed information about each process, such as CPU and memory usage.
Key Features and Interface
htop provides an enhanced interface compared to top, with the following notable features:
Interactive Commands
Navigation: Use arrow keys or mouse to navigate through the process list.
Process Management: Press F9 to kill a process, F7 to renice a process, F5 to sort processes, etc.
Filtering: Press F4 to search/filter processes by name.
Detailed Process Information: Displays detailed information about each process, including command line arguments and environment variables.
Color-coded Display: Different colors are used to highlight processes based on their resource usage.
Columns
PID: Process ID
USER: User running the process
%CPU: Percentage of CPU time used by the process
%MEM: Percentage of memory used by the process
COMMAND: Command name or command line used to start the process
TIME+: Total CPU time used by the process (in seconds)
Threads: Number of threads used by the process
Example:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1234 user 20 0 123456 7890 4567 R 10.0 2.0 0:05.12 htop
Options
-u <username>: Display processes for a specific user.
-p <PID>: Monitor specific process IDs.
-d <delay>: Set the delay between updates (in seconds).
-C: Sort by the command name rather than by CPU usage.
Example:
htop-uusername# Show processes for user 'username'htop-p1234,5678# Monitor processes with PID 1234 and 5678
Use Cases
Real-time Monitoring: htop is ideal for real-time monitoring of system processes and resource usage.
Process Management: Helps in managing processes interactively, such as killing or renicing processes based on their resource consumption.
Performance Analysis: Useful for troubleshooting performance issues and identifying processes that are consuming excessive CPU or memory.
Conclusion
htop is a feature-rich and user-friendly alternative to top, offering enhanced visualization and interactive capabilities for monitoring system processes on Unix-like systems. It provides detailed insights into CPU, memory, and process activity, making it a valuable tool for system administrators, developers, and users concerned with system performance and resource management. By leveraging its interactive commands and customizable options, users can effectively monitor, manage, and optimize system resources. help
Usage: head [OPTION]... [FILE]...
Print the first 10 lines of each FILE to standard output.
With more than one FILE, precede each with a header giving the file name.
With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
-c, --bytes=[-]NUM print the first NUM bytes of each file;
with the leading '-', print all but the last
NUM bytes of each file
-n, --lines=[-]NUM print the first NUM lines instead of the first 10;
with the leading '-', print all but the last
NUM lines of each file
-q, --quiet, --silent never print headers giving file names
-v, --verbose always print headers giving file names
-z, --zero-terminated line delimiter is NUL, not newline
--help display this help and exit
--version output version information and exit
NUM may have a multiplier suffix:
b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024,
GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.
Binary prefixes can be used, too: KiB=K, MiB=M, and so on.
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>
Full documentation <https://www.gnu.org/software/coreutils/head>
or available locally via: info '(coreutils) head invocation'
root@SAMANLEARN:~# ^C
root@SAMANLEARN:~# man head
root@SAMANLEARN:~# htop --help
htop 3.2.1
(C) 2004-2019 Hisham Muhammad. (C) 2020-2022 htop dev team.
Released under the GNU GPLv2+.
-C --no-color Use a monochrome color scheme
-d --delay=DELAY Set the delay between updates, in tenths of seconds
-F --filter=FILTER Show only the commands matching the given filter
-h --help Print this help screen
-H --highlight-changes[=DELAY] Highlight new and old processes
-M --no-mouse Disable the mouse
-p --pid=PID[,PID,PID...] Show only the given PIDs
--readonly Disable all system and process changing features
-s --sort-key=COLUMN Sort by COLUMN in list view (try --sort-key=help for a list)
-t --tree Show the tree view (can be combined with -s)
-u --user[=USERNAME] Show only processes for a given user (or $USER)
-U --no-unicode Do not use unicode but plain ASCII
-V --version Print version info
Long options may be passed with a single dash.
man
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 horizontally, and interact
using a pointing device (mouse). You can observe all processes running on the system,
along with their command line arguments, 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 entering 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 display 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-insen‐
sitive 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.
-u --user=USERNAME|UID
Show only the processes of a given user
-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; requires libcap support.
Drop unneeded Linux capabilities. In strict mode features like killing, changing
process priorities, and reading process delay accounting information will not work,
due to less capabilities 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 enable 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 nec‐
essary.
Down, Alt-j
Select (highlight) the next process in the process list. Scroll the list if neces‐
sary.
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 high‐
lighted one.
c Tag the current process and its children. Commands that can operate on multiple pro‐
cesses, 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, 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.
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 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, press‐
ing F3 will cycle through matching occurrences. Pressing Shift-F3 will cycle back‐
wards.
Alternatively the search can be started by simply typing the command 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 pro‐
cesses whose names match will be shown. To cancel filtering, enter the Filter option
again and press Esc. The matching 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 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, <, >
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'
Shift-F8, {
Decrease the selected process's autogroup priority (add to autogroup 'nice' value)
F9, k
"Kill" process: sends a signal which is selected in a menu, to one or a group of pro‐
cesses. 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.
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