Commands by em (3)

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commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

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Check if a command is available in your system
Usefull to detect if a commad that your script relies upon is properly installed in your box, you can use it as a function function is_program_installed() { type "$1" >/dev/null } Invoke it and check the execution code is_program_installed "dialog" if [ ! $? -eq 0 ]; then echo "dialog is not installed" exit 1 fi

Test your bash skills.

Disable sleep mode via cli and systemd (Centos, Debian Ubuntu?)
This causes computer to never power off or go into sleep mode. Disables sleep mode linux.

Show CPU usage for EACH cores

Set all CPU cores' CPU frequency scaling governor to maximum performance

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Ping Twitter to check if you can connect
Returns a JSON object, by connecting to the 'test' endpoint of the Twitter API. Simplest way to check if you can connect to Twitter. Output also available in XML, use '/help/test.xml' for that

Display the output of a command from the first line until the first instance of a regular expression.
If BREs can be used, this sed version will also get the job done.

All what exists in dir B and not in dir A will be copied from dir B to new or existing dir C
Assumed dir A, B, C are subdirs of the current dir Exact syntax of the command is: rsync -v -r --size-only --compare-dest=/path_to_A/A/ /path_to_B/B/ /path_to_C/C/ (do not omit end-slashes, since that would copy only the names and not the contents of subdirs of dir B to dir C) You can replace --size-only with --checksum for more thorough file differences validation Useful switch: -n, --dry-run perform a trial run with no changes made

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"


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