# man > watch(1) > **TLDR:** Execute a program periodically and monitor the output in full-screen mode. > - Repeatedly run a command and show the result: `watch {{command}}` - Re-run a command every 60 seconds: `watch {{-n|--interval}} 60 {{command}}` - Monitor disk space, highlighting differences as they appear: `watch {{-d|--differences}} df` - Repeatedly run a pipeline and show the result: `watch "{{command1}} | {{command2}} | {{command3}}"` - Exit `watch` if the visible output changes: `watch {{-g|--chgexit}} {{lsblk}}` - Interpret terminal control characters: `watch {{-c|--color}} {{ls --color=always}}` *Source: tldr-pages* --- [WATCH(1)](https://www.chedong.com/phpMan.php/man/WATCH/1/markdown) User Commands [WATCH(1)](https://www.chedong.com/phpMan.php/man/WATCH/1/markdown) ## NAME watch - execute a program periodically, showing output fullscreen ## SYNOPSIS **watch** [_options_] _command_ ## DESCRIPTION **watch** runs _command_ repeatedly, displaying its output and errors (the first screenfull). This allows you to watch the program output change over time. By default, _command_ is run every 2 seconds and **watch** will run until interrupted. ## OPTIONS ### -d --differences Highlight the differences between successive updates. If the optional _permanent_ argu‐ ment is specified then **watch** will show all changes since the first iteration. ### -n --interval Specify update interval. The command will not allow quicker than 0.1 second interval, in which the smaller values are converted. Both '.' and ',' work for any locales. The WATCH_INTERVAL environment can be used to persistently set a non-default interval (following the same rules and formatting). ### -p --precise Make **watch** attempt to run _command_ every **--interval** _seconds_. Try it with **ntptime** (if present) and notice how the fractional seconds stays (nearly) the same, as opposed to normal mode where they continuously increase. ### -t --no-title Turn off the header showing the interval, command, and current time at the top of the display, as well as the following blank line. ### -b --beep Beep if command has a non-zero exit. ### -e --errexit Freeze updates on command error, and exit after a key press. ### -g --chgexit Exit when the output of _command_ changes. ### -c --color Interpret ANSI color and style sequences. ### -x --exec Pass _command_ to [**exec**(2)](https://www.chedong.com/phpMan.php/man/exec/2/markdown) instead of **sh** **-c** which reduces the need to use extra quoting to get the desired effect. ### -w --no-linewrap Turn off line wrapping. Long lines will be truncated instead of wrapped to the next line. ### -h --help Display help text and exit. ### -v --version Display version information and exit. ## EXIT STATUS **0** Success. **1** Various failures. **2** Forking the process to watch failed. **3** Replacing child process stdout with write side pipe failed. **4** Command execution failed. **5** Closing child process write pipe failed. **7** IPC pipe creation failed. **8** Getting child process return value with [**waitpid**(2)](https://www.chedong.com/phpMan.php/man/waitpid/2/markdown) failed, or command exited up on error. **other** The watch will propagate command exit status as child exit status. ## ENVIRONMENT The behaviour of **watch** is affected by the following environment variables. **WATCH**___**INTERVAL** Update interval, follows the same rules as the **--interval** command line option. ## NOTES POSIX option processing is used (i.e., option processing stops at the first non-option argu‐ ment). This means that flags after _command_ don't get interpreted by **watch** itself. ## BUGS Upon terminal resize, the screen will not be correctly repainted until the next scheduled up‐ date. All **--differences** highlighting is lost on that update as well. Non-printing characters are stripped from program output. Use **cat** **-v** as part of the command pipeline if you want to see them. Combining Characters that are supposed to display on the character at the last column on the screen may display one column early, or they may not display at all. Combining Characters never count as different in **--differences** mode. Only the base character counts. Blank lines directly after a line which ends in the last column do not display. **--precise** mode doesn't yet have advanced temporal distortion technology to compensate for a _command_ that takes more than **--interval** _seconds_ to execute. **watch** also can get into a state where it rapid-fires as many executions of _command_ as it can to catch up from a previous exe‐ cutions running longer than **--interval** (for example, **netstat** taking ages on a DNS lookup). ## EXAMPLES To watch for mail, you might do watch -n 60 from To watch the contents of a directory change, you could use watch -d ls -l If you're only interested in files owned by user joe, you might use watch -d 'ls -l | fgrep joe' To see the effects of quoting, try these out watch echo $$ watch echo '$$' watch echo "'"'$$'"'" To see the effect of precision time keeping, try adding **-p** to watch -n 10 sleep 1 You can watch for your administrator to install the latest kernel with watch uname -r (Note that **-p** isn't guaranteed to work across reboots, especially in the face of **ntpdate** (if present) or other bootup time-changing mechanisms) procps-ng 2020-12-06 [WATCH(1)](https://www.chedong.com/phpMan.php/man/WATCH/1/markdown)