basic shell commands

Created at 2014-06-25 Updated at 2023-03-08 Category work Tag shell / terminal / ubuntu

  • cat - Send a file to the screen in one go. Useful for piping to other programs
    cat file1 # list file1 to screen
    cat file1 file2 file3 > outfile # add files together into outfile
    cat *.txt > outfile # add all .txt files together
    cat file1 file2 | grep fred # pipe files

  • cc - Compile a C program
    cc test1.c # compile test1.c to a.out
    cc -O2 -o test2.prog test2.c # compile test2.c to test2.prog

  • cd - Change current directory
    cd # go to home directory
    cd ~/papers # go to /home/user/papers
    cd ~fred # go to /home/fred
    cd dir # go to directory (relative)
    cd /dir1/dir2/dir3… # go to directory (absolute)
    cd - # go to last directory you were in

  • cp - Copy file(s)
    cp file1 file2 # copy file1 to file2
    cp file1 directory # copy file1 into directory
    cp file1 file2 file3 … directory # copy files into directory
    cp -R dir1 dir2/ # copy dir1 into dir2 including subdirectries
    cp -pR dir1 dir2/ # copy directory, preserving permissions

  • date - Shows current date

  • emacs - The ubiquitous text editor
    emacs foo.txt # open file in emacs

  • file - Tells you what sort of file it is
    > file temp_70.jpg
    temp_70.jpg: JPEG image data, JFIF standard 1.01,
    resolution (DPI), 72 x 72

  • firefox - Start Mozilla Firefox

  • gedit - Gnome text editor

  • grep - Look for text in files. List out lines containing text (with filename if more than one file examined).
    grep “hi there” file1 file2 … # look for ‘hi there’ in files
    grep -i “hi there” filename # ignore capitals in search
    cat filename | grep “hi there” # use pipe
    grep -v “foo” filename # list lines that do not include foo

  • gtar - GNU version of the tar utility (also called tar on Linux). Store directories and files together into a single archive file. Use the normal tar program to backup files to a tape. See info tar for documentation.
    gtar cf out.tar dir1 # put contents of directory into out.tar
    gtar czf out.tar.gz dir1 # write compressed tar, out.tar.gz
    gtar tf in.tar # list contents of in.tar
    gtar tzf in.tar.gz # list contents of compressed in.tar.gz
    gtar xf in.tar # extract contents of in.tar here
    gtar xzf in.tar.gz # extract compressed in.tar.gz
    gtar xf in.tar file.txt … # extract file.txt from in.tar

  • gzip / gunzip - GNU Compress files into a smaller space, or decompress .Z or .gz files.
    gzip file.fits # compresses file.fits into file.fits.gz
    gunzip file.fits.gz # recovers original file.fits
    gzip .dat # compresses all .dat files into .dat.gz
    .dat.gz # decompresses all .dat.gz files into .dat
    program | gzip > out.gz # compresses program output into out.gz
    program | gunzip > out # decompresses compressed program output

  • info - A documentation system designed to replace man for GNU programs (e.g. gtar, gcc). Use cursor keys and return to go to sections. Press b to go back to previous section. A little hard to use.
    info gtar # documentation for gtar

  • kill - Kill, pause or continue a process. Can also be used for killing daemons.
    > ps -u jss

    666 pts/1 06:06:06 badprocess
    > kill 666 # this sends a nice’’ kill to the

    process. If that doesn’t work do

    > kill -KILL 666 # (or equivalently)
    > kill -9 666 # which should really kill it!

> kill -STOP 667 # pause (stop) process
> kill -CONT 667 # unpause process

  • latex - Convert a tex file to dvi

  • logout - Closes the current shell. Also try exit’’.

  • lp - Sends files to a printer
    lp # sends postscript file to the default printer
    lp -dlp2 # sends file to the printer lp2
    lp -c # copies file first, so you can delete it
    lpstat -p lp2 # get status and list of jobs on lp2
    cancel lp2-258 # cancel print job lp2-258

lpr -Plp2 # send to lp2
lpq -Plp2 # get list of jobs on lp2
lprm -Plp2 1234 # delete job 1234 on lp2

  • ls - Show lists of files or information on the files
    ls file # does the file exist?
    ls -l file # show information about the file
    ls *.txt # show all files ending in .txt
    ls -lt # show information about all files in date order
    ls -lrt # above reversed in order
    ls -a # show all files including hidden files
    ls dir # show contents of directory
    ls -d dir # does the directory exist?
    ls -p # adds meaning characters to ends of filenames
    ls -R # show files also in subdirectories of directory
    ls -1 # show one file per line

  • man - Get instructions for a particular Unix command or a bit of Unix. Use space to get next page and q to exit.
    man man # get help on man
    man grep # get help on grep
    man -s1 sort # show documentation on sort in section 1

  • more - Show a file one screen at a time
    more file # show file one screen at a time
    grep ‘frog’ file | more # Do it to output of other command

  • mv - Move file(s) or rename a file
    mv file1 file2 # rename file1 to file2
    mv dir1 dir2 # rename directory dir1 to dir2
    mv file1 file2 file3 … directory # move files into directory

  • nano - very simple text editor. Warning - this program can introduce extra line breaks in your file if the screen is too narrow!

  • nice - Start a process in a nice way. Nice levels run from -19 (high priority) to 19 (low priority). Jobs with a higher priority get more CPU time. See renice for more detail. You should probably be using the grid-engine to run long jobs.
    nice +19 myjob1 # run at lowest priority
    nice +8 myjob2 # run at lowish priority

  • - a free office suite available for Linux/Unix, Windows and Mac OS X.

  • passwd - change your password

  • pine - A commonly used text-based mail client. It is now called alpine. Allows you to send and receive emails. Configuration options allow it to become quite powerful. Other alternatives for mail are mozilla mail and mutt, however I suggest you stick to alpine or thunderbird.

  • printenv - Print an environment variable in tcsh
    setenv MYVARIABLE Fred
    printenv MYVARIABLE
    printenv # print all variables

  • ps - List processes on system
    > ps -u jss # list jss’s processes
    934 pts/0 00:00:00 bash

PID output CPU time name
> ps -f # list processes started here in full format
> ps -AF # list all processes in extra full format
> ps -A -l # list all processes in long format
> ps -A | grep tcsh # list all tcsh processes

  • pwd - Show current working directory
    > pwd

  • quota - Shows you how much disk space you have left
    > quota -v

  • rm - Delete (remove) files
    rm file1 # delete a file (use -i to ask whether sure)
    rm -r dir1 # delete a directory and everything in it (CARE!)
    rm -rf dir1 # like above, but don’t ask if we have a -i alias

rmdir - Delete a directory if it is empty (rm -r dirname is useful if it is not empty)

rmdir dirname

  • top - Interactively show you the top'' processes on a system - the ones consuming the most computing (CPU) time. Press theq’’ key in top to exit. Press the k'' key to kill a particular process. Pressr’’ to renice a process.
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