Linux commands

Linux
Basic Commands
Y.Shashidhar
shashi@cse.iitb.ac.in

Basic Linux Commands
• File Handling
• Text Processing
• System Administration
• Process Management
• Archival
• Network
• File Systems
• Advanced Commands

Sources to learn commands??


Primary – man(manual) pages.






man <command>   shows all information about the
command
<command> help   shows the available options
for that command

Secondary – Books and Internet

File Handling commands

• mkdir – make directories
         Usage: mkdir [OPTION] DIRECTORY...
        eg. mkdir prabhat

• ls – list directory contents
        Usage: ls [OPTION]... [FILE]...
        eg. ls, ls l, ls prabhat

• cd – changes directories
        Usage: cd [DIRECTORY]
        eg. cd prabhat

File Handling(contd...)

• pwd   print name of current working directory
      Usage: pwd

• vim – Vi Improved, a programmers text editor
      Usage: vim [OPTION] [file]...
      eg. vim file1.txt



cp – copy files and directories

         Usage: cp [OPTION]... SOURCE DEST

         eg. cp sample.txt sample_copy.txt
               cp sample_copy.txt target_dir


mv – move (rename) files

        Usage: mv [OPTION]... SOURCE DEST

        eg. mv source.txt target_dir
              mv old.txt new.txt

• rm remove files or directories
         Usage: rm [OPTION]... FILE...
         eg. rm file1.txt , rm rf some_dir

• find – search for files in a directory hierarchy
        Usage: find [OPTION] [path] [pattern]
        eg. find file1.txt, find name file1.txt
• history – prints recently used commands
         Usage: history

Pattern
A Pattern is an expression that describes a set of
strings which is used to give a concise description
of a set, without having to list all elements.
eg. ab*cd matches anything that starts with ab and
ends with cd etc.
ls *.txt – prints all text files

Text Processing

• cat – concatenate files and print on the standard output
     Usage: cat [OPTION] [FILE]...
     eg. cat file1.txt file2.txt

         cat n file1.txt

• echo – display a line of text
     Usage: echo [OPTION] [string] ...
     eg. echo I love India
           echo $HOME

Text Processing(contd...)

• grep print lines matching a pattern
    Usage: grep [OPTION] PATTERN [FILE]...
    eg. grep i apple sample.txt


• wc print the number of newlines, words, and bytes in files
     Usage: wc [OPTION]... [FILE]...
     eg.  wc file1.txt
            wc L file1.txt

Text Processing(contd...)
• sort – sort lines of text files
     Usage: sort [OPTION]... [FILE]...
     eg. sort file1.txt
         sort r file1.txt

Linux File Permissions

• 3 types of file permissions – read, write, execute
• 10 bit format from 'ls l' command
                 1             2 3 4      5 6 7     8 9 10
             file type    owner     group    others
eg. drwxrwr   means owner has all three permissions,
      group has read and write, others have only read
  permission
• read permission – 4, write – 2, execute 1
        eg. rwxrwr   = 764
              673    =   rwrwxwx

System Administration

• chmod – change file access permissions
       Usage: chmod [OPTION] [MODE] [FILE]
      eg. chmod 744 calculate.sh

• chown – change file owner and group
      Usage: chown [OPTION]... OWNER[:[GROUP]] FILE...
      eg. chown remo myfile.txt

System Administration (contd...)
•  su –  change user ID or become superuser
       Usage: su [OPTION] [LOGIN]
       eg. su remo, su
• passwd – update  a user’s authentication tokens(s)
       Usage: passwd [OPTION]
       eg. passwd
• who – show who is logged on
       Usage: who [OPTION]
       eg. who , who b , who q

Process Management

• ps – report a snapshot of the current processes
     Usage: ps [OPTION]
     eg. ps,  ps el

• kill – to kill a process(using signal mechanism)
     Usage: kill [OPTION] pid
     eg. kill 9 2275

Archival

• tar – to archive a file
      Usage: tar [OPTION] DEST SOURCE
      eg. tar cvf /home/archive.tar /home/original
            tar xvf /home/archive.tar

• zip – package and compress (archive) files
      Usage: zip [OPTION] DEST SOURSE
      eg. zip original.zip original
• unzip – list, test and extract compressed files in a ZIP archive
     Usage: unzip filename
        eg. unzip original.zip

Network

• ssh – SSH client (remote login program)
    “ssh is a program for logging into a remote machine and for
   executing commands on a remote machine”
Usage: ssh [options] [user]@hostname

eg. ssh X guest@10.105.11.20
• scp – secure copy (remote file copy program)
          “scp copies files between hosts on a network”
Usage: scp [options] [[user]@host1:file1] [[user]@host2:file2]
eg. scp file1.txt guest@10.105.11.20:~/Desktop/

File Systems
• fdisk – partition manipulator
     eg. sudo fdisk l
• mount – mount a file system
    Usage: mount t type device dir
    eg. mount /dev/sda5 /media/target
• umount – unmount file systems
    Usage: umount [OPTIONS] dir | device...
    eg.  umount /media/target

File Systems(contd...)

• du – estimate file space usage
     Usage:  du [OPTION]... [FILE]...
     eg. du

• df – report filesystem disk space usage
    Usage: df [OPTION]... [FILE]...
    eg. df

• quota – display disk usage and limits
    Usage: quota [OPTION]
    eg. quota v

Advanced Commands
• reboot – reboot the system
       Usage: reboot [OPTION]
     eg. reboot

• poweroff – power off the system
       Usage: poweroff [OPTION]
     eg. poweroff

Suggested Material
• The UNIX Programming Environment
by Kernighan and Pike (PrenticeHall)
• Your UNIX: The Ultimate Guide
by Sumitabha Das

Editor commands

• kate – KDE Advanced Text Editor
      Usage:  kate [options][file(s)]
      eg. kate file1.txt file2.txt

• vim – Vi Improved, a programmers text editor
      Usage: vim [OPTION] [file]...
      eg. vi hello.c

• gedit A text Editor. Used to create and edit files.
               Usage: gedit [OPTION] [FILE]...
               eg. gedit

Process Management(contd...)
• bg – make a foreground process to run in background
         Usage: type 'ctrl+z'  and then 'bg <job id>'
• fg – to make background process as foreground process
          Usage: fg [jobid]
• jobs – displays the names and ids of background jobs
          Usage: jobs

Advanced Commands (contd...)
• sed   stream editor for filtering and transforming text
    Usage: sed [OPTION] [inputfile]...
    eg. sed 's/love/hate/g' loveletter.txt

• awk pattern scanning and processing language
    eg.  awk F: '{ print $1 }' sample_awk.txt

• find search for files in a directory hierarchy
                    Usage: find [OPTION] [path] [pattern]
                                    eg. find name file1.txt
• locate – find or locate a file
     Usage: locate [OPTION]... FILE...
     eg. locate file1.txt

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