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---+++ Linux Workshop

---++++ Helpful Command Line Utilities

---++++ July 27, 2005


---++ Quick Special Symbols Primer
   * =~= - expands to your home directory (Example: =cd ~=)
   * =.= - expands to the current directory (Example: =ls .=)
   * =..= - expands to the parent directory (Example: =ls ..=)

---++ Getting Help
   * =help= - bash command-line/scripting help
   * =apropos= - use this if you're looking for a command that does &lt;insert task here&gt; (Example: =apropos edit=)
   * =man= - looks up help files for various commands (Example: =man grep=)
   * =info= - opens an emacs-like interface for extensive guides to commands (Example: =info make=)
   * =whatis= - shows a quick overview of the command (Example: =whatis ls=)

---++ Nifty Bash Commands
   * =pushd= and =popd= - quick directory traversal%BR%
      * Example:%BR%
           =cd ~= %BR%
           =pushd /usr/share/doc= %BR%
           =pushd= %BR%
           =popd= 
      * You can also =cd -= to change to the directory you were just in.
   * =alias= - command aliasing%BR%
      * Example:%BR%
        =alias -p= %BR%
        =alias changecd="eject; sleep 5; eject -t"= %BR%
        =changecd=
   * control-r - reverse search
   * ~/.bashrc can be used to automatically add aliases

---++ Nifty File Manipulation Tools
   * =grep= - string searching in files
      * lots of different options (Use =grep --help= or =man grep= to see them all)
      * ways of calling grep: =grep=, =egrep=, =rgrep=
      * Examples:
         * =grep -v apple fruits.txt=
         * =egrep '.*berry.*' fruits.txt=
         * =rgrep a *= (recursive search)
   * =wc= - count the number of letters, words, and paragraphs in a file
   * =cat= - print out a file's contents
   * =sort= - sort a file alphabetically or numerically (Example: =sort -r vegetables.txt=)
   * =tail= - print the last few lines of a file
   * =head= - print the first few lines of a file
   * =uniq= - remove (sequential) duplicate lines in a file (Example: =uniq names.txt=)
      * You can use sort and uniq together to quickly tidy up files.
      * Example: =sort names.txt | uniq= (see [[#PiPiNg][Piping]] below)
   * =sed= - regular expression/scripting tool
      * Regular expressions are a way to flexibly match/replace text.
      * Example: =sed -r -e 's/tomato/squash/' vegetables.txt= (replaces all occurrances of "tomato" with "squash")
   * Handy console text editors:
      * =vim= 
      * =emacs=
      * =nano=

---++ Nifty File Searching Tools
   * =ls= - list directory contents
   * =find= - a tool for recursive directory searching
      * Many options, check out =man find= or =find --help= to see them all.
      * Example: =find . -iname '*.log'= (will list all files/directories contained in the current directory (".") that match the pattern "*.log" (case-insensitive))
   * =locate= - a simple tool for finding files system-wide
      * *Note*: you _may_ need to run =updatedb= (as root) first before you use =locate= (especially if you're searching for a new file), but many Linux systems automatically run this command on a daily basis.
      * Example: =locate apache=
   * =whereis= - shows the full directory path to a command you're looking for (Example: =whereis bash=)

---++ Nifty Commands Related to Processes and Running Applications
   * =ps= - view running processes
      * Run with no options, =ps= shows the user's processes.
      * To show all processes, type something like this: =ps -ax=
   * =pstree= - view running processes in a tree format
   * =killall= - kill errant processes (_use with caution!_) (Example: =killall kwrite=) 
   * =nice= - run a process at a different priority level
      * Use =nice= if you want a costly program to use up less of your system resources.
      * You can also use =nice= to boost the priority of a process (see =man nice=)
      * Example: =nice find / -name '*'=
   * =lsof= - show which files processes are using (helpful for umounting)

---++ Nifty Disk Usage Utilities
   * =df= - show disk usage on all mounted drives (Example: =df -h=)
   * =du= - show disk usage in a specified directory (Example: =du . -sh=)
   * =mount= - mount a device to a directory (see =man mount= for complete instructions)
      * Can mount devices such as the CD-ROM drive, USB memory stick, or iPod to a specified directory.
      * Type =mount= with no arguments to see what devices are mounted.
      * Run =umount= to unmount a drive.

---++ Nifty Printing Utilities
   * =lpstat= - show information about printers (Example: =lpstat -p=)
   * =lpr= - print files from the command line (Example: =lpr -P laser1 fruits.txt=)

---++ Other Nifty Commands
   * =lynx= - console web browser
   * =bc= - math interpreter (Example: =echo 5*6/3+23 | bc=)
   * =cal= - calendar (Example: =cal -3=)

---++ Commands Just For Fun
   * =fortune= - random quotes and witty sayings (install by running =apt-get install fortune= as root)
      * Example quotes from =fortune=:
         * Abandon the search for Truth; settle for a good fantasy.
         * Celebrate Hannibal Day this year.  Take an elephant to lunch.
      * Install the "fortunes" package for extra fortunes (run =apt-get install fortunes= as root)
         * Examples:
            * =fortune startrek= - "Live long and prosper." -- Spock, "Amok Time", stardate 3372.7
            * =fortune linux= - "Why use Windows when you can have air conditioning? Why use Windows, when you can leave through the door?" -- Konrad Blum
   * =scrabble= - a text-based scrabble game (installation: =apt-get install scrabble=)
   * =adventure= - a text-based roleplaying game (installation: =apt-get install bsdgames=)

#PiPiNg
---++ Piping and Redirecting Output
   * Many commands that run in the console can redirect their output to a file or another program using special characters.
   * Redirecting output
      * =>=, =>>=, and =&>=
         * =>= will *truncate* any file that you specify before outputting.
         * =>>= will append output to a file.
         * =&>= will *truncate* and send both normal and error messages to a file.
      * Make sure you don't use =>= when you mean =>>=!
      * Examples:
         * =sort names.txt > sorted-names.txt=
         * =cat vegetables.txt >> fruits.txt=
         * =grep &> grep-error.txt=
   * Piping
      * Use the =|= symbol to pipe output.
      * Examples:
         * =sort names.txt | uniq=
         * =sort vegetables.txt | egrep '^c' | wc=

---++ Other resources
   * [[http://www.linuxgazette.com/node/8856][Command Line Essentials]]
   * [[http://www.tuxfiles.org/linuxhelp/cli.html][Command Line Tutorials]]

Topic attachments
I	Attachment	Action	Size	Date	Who	Comment
txt	fruits.txt	manage	0.1 K	25 Jul 2005 - 14:16	JeremyStephens	List of fruits
txt	names.txt	manage	0.6 K	25 Jul 2005 - 14:36	JeremyStephens	List of common names
txt	vegetables.txt	manage	0.1 K	25 Jul 2005 - 14:30	JeremyStephens	List of vegetables

Topic revision: r4 - 27 Jul 2005, JeremyStephens

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