Old UCOTD's: Unix Commands of the Day

cd - Change working directory

Monday, Nov 24, 1997


Usage: cd [ <dir> ]

Unix uses a "shell" is its main user interface. In the shell, you type commands (like the ones found on this door) to manipulate files. Since there are often lots of files in a system, it is handy to have a working directory. The default is your home directory. cd alone in many shells takes you to your home directory, also know as ~ in many of those same shells. ~<user> is that user's home directory.

.. - is the directory above the current directory
. - is the current directory


eg. cd ..

grep - get regular expression and print

Wed Nov 19, 1997


Usage: grep [ options ] <pattern> [ <file1>> [ <file2> ] ]

grep prints lines in the standard input (or from the given file(s)) that contain the specified pattern.

v - print lines that do not contain the pattern
c - count the lines instead of printing them
n - output line numbers with the lines containing the pattern
i - ignore case is the pattern


eg. grep -c ';' *.c

cat - concatenate and display files

Tue Nov 18, 1997


Usage: cat [ options ] [ <file1> [ <file2> ] ]

cat has options but no one really uses them


eg. cat ucotd.html >> prev.ucotd.html

ps - report processor status

Mon Nov 17 12:29:37 EST 1997


Usage: ps [ auxw ]

a - include any process with a controlling terminal (not just your processes)
u - include user name and start time
x - include processes without controlling terminals (includes other users w/a)
w - wide format; every w adds a possible line per process, linux supports up to 100 w's


eg. ps aux | grep -v grep | grep soren

Use man <command> for more info...above is only a brief summary.