whereis

whereis

Search $path, man pages and source files for an application file. The supplied filenames are first stripped of leading pathname components and any (single) trailing extension of the form .ext (for example, .c). Prefixes of s. resulting from use of … Continued
which

which

Locate a program file in the user’s path. For each of its arguments which prints to stdout the full path of the executable(s). It does this by searching the directories listed in the environment variable PATH. Syntax which [options] [--] … Continued
while

while

Execute consequent-commands as long as test-commands has an exit status of zero Syntax while test-commands; do consequent-commands; done The while command continuously executes the do consequent-commands as long as the last command in test-commands returns an exit status of zero. The return status is the exit status of the last … Continued
who

who

Print who is currently logged in Syntax who [options] [file] [am i] Options -m Print the current user id, name and domain (Same as `who am i') -q --count Print only the login names and the number of users logged … Continued
whoami

whoami

Print the current user id and name. Same as id -un. Syntax whoami [options] Options --help Display Help --version Display program version info The whoami utility has been obsoleted by the id(1) utility, and is equivalent to ‘id -un’. The command id … Continued
write

write

Send a message to another user. Syntax: write user [ttyname] Write allows you to communicate with other users, by copying lines from your terminal to theirs. When you run the write command, the user you are writing to gets a … Continued
xargs

xargs

Execute a command, passing constructed argument list(s). The arguments are typically a long list of filenames (generated by ls or find) that are passed to xargs via a pipe. Syntax xargs [options] [command] Options --arg-file=file -a file Read items from file instead of … Continued
xdg-open

xdg-open

Open a file or URL in the user’s preferred application. Syntax xdg-open file xdg-open URL xdg-open --help xdg-open --manual xdg-open --version Options: files The filename(s) to open, wildcards are accepted. If a URL is provided the URL will be opened … Continued
xz

xz

xz, unxz, xzcat, lzma, unlzma, lzcat – Compress or decompress .xz and .lzma files Syntax xz [option]... [file]... unxz is equivalent to xz --decompress. xzcat is equivalent to xz --decompress --stdout. lzma is equivalent to xz --format=lzma. unlzma is equivalent … Continued
yes

yes

Print the command line argument(s), separated by spaces and followed by a newline, forever until killed. When piped into a command, it will continue until the pipe breaks (i.e., the program completes its execution). Syntax yes text yes --help yes … Continued