Linux Commands

Linux User Group @ SJSU Linux Commands (Find PocMan on lug-sjsu.org)

Linux User Group at San Jose State University BASH – Bourne Again Shell What is a Shell? Customizing the environment - Local and Environment variables HOME, SHELL, PS1 PATH, LD_LIBRARY_PATH - Aliases alias ll=‘ls –l’ - Command history history, !!, !# - Initialization Scripts .bashrc file

Linux User Group at San Jose State University BASH contd. Redirecting standard input < standard output > standard error 2> Pipes | Command Substitution `` Wild-Cards * ? [ijk] [!ijk] [x-z]

Linux User Group at San Jose State University Basic File System commands cd – Changing the current directory ls – Listing directory contents mkdir – Making directories rmdir – Removing directories pwd – Checking current directory

Linux User Group at San Jose State University Basic File commands cat – Displaying file contents cp – Copying a file mv – Renaming files rm – Removing files file – Knowing the file types Soft and Hard links

Linux User Group at San Jose State University Backing up files gzip - Compressing Files gunzip - Decompressing Files tar – Archival program

Linux User Group at San Jose State University Basic File Attributes Listing file attributes `ls -l` File Ownership File Permissions Directory Permissions chmod – Changing File ownership

Linux User Group at San Jose State University The Process Basics process commands ps, pstree, top Process states ‘ ctrl z’ – suspend a process ‘ ctrl c’ - kill a process Runnning Jobs in Background '&' , bg, fg kill - Killing Processes with Signals

Linux User Group at San Jose State University Networking commands/tools Checking the network ping, traceroute, ifconfig, netstat DNS host, nslookup, dig Remote Login telnet, ssh

Linux User Group at San Jose State University Miscellaneous commands man & info who, whoami touch finger, finger <username> whereis, which df, du shutdown

Vi vi filename [count][command] (count repeats the effect of the command) Vi starts in command mode. The positioning commands operate only while vi is in command mode. You switch vi to input mode by entering any one of several vi input commands. Once in input mode, any character you type is taken to be text and is added to the file. You cannot execute any commands until you exit input mode. To exit input mode, press the escape ( Esc ) key. Linux User Group at San Jose State University

grep What Is grep? Grep is a tool that originated from the UNIX world during the 1970's. It can search through files and folders (directories in UNIX) and check which lines in those files match a given regular expression. Grep will output the filenames and the line numbers or the actual lines that matched the regular expression. All in all a very useful tool for locating information stored anywhere on your computer, even (or especially) if you do not really know where to look.

grep contd.. grep -i – ignores case grep -A Num– prints Num lines after context grep -B Num– prints Num lines before context grep -C Num – prints Num lines around context

Grep contd.. grep -c – returns count of matching lines grep -H – return filenames in which match is found. grep -d type – searching in directories. Where type can be one of the following skip (skip directories specified) recurse (iterate into directories search each file in the directory) read (read directories)

Grep contd.. Regular Expressions [ ] - range of characters * - matches zero or more times + - matches one or more times ^ - beginning of line $ - end of line ? - match is optional and matches at most once {n} – matches n occurrence

Cut To extract information from section from each line of input (usually files) Extraction can be done based on -b – bytes -c – characters -f – fields -d – delimiter (default is tab)

Cut contd.. A range must be provided in order to extract informations. -N – to end of line -M – from beginning of line till M Usually N and M are counted from 1 (not 0). If we specify 0, latest version errors out but previous versions assumes it to be 1.

03/09/10 Linux User Group at San Jose State University By Rohit Surve and Harish Krishnan

Linux Commands

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