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grep is a command-line utility for searching plaintext datasets for lines that match a regular expression.Its name comes from the ed command g/re/p (global regular expression search and print), which has the same effect.
He later added this capability to the Unix editor ed, which eventually led to the popular search tool grep's use of regular expressions ("grep" is a word derived from the command for regular expression searching in the ed editor: g/re/p meaning "Global search for Regular Expression and Print matching lines"). [15]
xargs (short for "extended arguments") [1] is a command on Unix and most Unix-like operating systems used to build and execute commands from standard input. It converts input from standard input into arguments to a command. Some commands such as grep and awk can take input either as
pgrep is a command-line utility initially written for use with the Solaris 7 operating system by Mike Shapiro.It has since been available in illumos and reimplemented for the Linux and BSDs (DragonFly BSD, FreeBSD, NetBSD, and OpenBSD).
In Unix-like operating systems, true and false are commands whose only function is to always return with a predetermined exit status.Programmers and scripts often use the exit status of a command to assess success (exit status zero) or failure (non-zero) of the command.
Another common case where cat is unnecessary is where a command defaults to operating on stdin, but will read from a file, if the filename is given as an argument. This is the case for many common commands; the following examples cat file | grep pattern cat file | less can instead be written as grep pattern file less file
The Unix egrep (extended grep) command can be used to print filenames of Unix or DOS files (assuming Unix and DOS-style files only, no classic Mac OS-style files): $ egrep -L '\r\n' myfile.txt # show UNIX style file (LF terminated) $ egrep -l '\r\n' myfile.txt # show DOS style file (CRLF terminated)
This is a list of POSIX (Portable Operating System Interface) commands as specified by IEEE Std 1003.1-2024, which is part of the Single UNIX Specification (SUS). These commands can be found on Unix operating systems and most Unix-like operating systems.