Sunday, 17 June 2012

Basic Linux Commands


1).TOUCH
NAME
       touch - change file timestamps
SYNOPSIS
       touch [OPTION]... FILE...
DESCRIPTION
       Update  the  access  and modification times of each FILE to the current
       time.
       -a     change only the access time
       -c, --do not create any files
       -d, --date=STRING
              parse STRING and use it instead of current time
       -f     (ignored)

2).CAT
NAME
       cat - concatenate files and print on the standard output
SYNOPSIS
       cat [OPTION] [FILE]...
DESCRIPTION
       Concatenate FILE(s), or standard input, to standard output.
       -A, --show-all  equivalent to -vET
       -b, --number-nonblank
              number nonblank output lines
       -e     equivalent to -vE
       -E, --show-ends
              display $ at end of each line
       -n, --number
              number all output lines

3).LS
NAME
       ls - list directory contents
SYNOPSIS
       ls [OPTION]... [FILE]...
DESCRIPTION
       List  information  about  the FILEs (the current directory by default).
       Sort entries alphabetically if none of -cftuvSUX nor --sort.
       Mandatory arguments to long options are  mandatory  for  short  options too.
       -a, --all
              do not ignore entries starting with .
       -A, --almost-all
              do not list implied . and ..
       --author
              with -l, print the author of each file

4).MKDIR
NAME
       mkdir - make directories
SYNOPSIS
       mkdir [OPTION] DIRECTORY...
DESCRIPTION
       Create the DIRECTORY(ies), if they do not already exist.
       Mandatory  arguments  to  long  options are mandatory for short options too.
       -Z, --context=CONTEXT (SELinux) set security context to CONTEXT
       -m, --mode=MODE
              set permission mode (as in chmod), not rwxrwxrwx - umask
       -p, --parents
              no error if existing, make parent directories as needed
       -v, --verbose
              print a message for each created directory

5).RMDIR
NAME
       rmdir - remove empty directories
SYNOPSIS
       rmdir [OPTION]... DIRECTORY...
DESCRIPTION
       Remove the DIRECTORY(ies), if they are empty.
       --ignore-fail-on-non-empty
              ignore  each  failure  that  is  solely  because  a directory is non-empty
       -p, --parents
              Remove DIRECTORY and its ancestors.  E.g., 'rmdir -p  a/b/c'  is similar to 'rmdir a/b/c a/b a'.
       -v, --verbose
              output a diagnostic for every directory processed
       --help display this help and exit

6).cd
BASH_BUILTINS(1)                                             
NAME
       bash,  :,  ., [, alias, bg, bind, break, builtin, cd, command, compgen,
       complete, continue, declare, dirs, disown, echo,  enable,  eval,  exec,
       exit,  export,  fc,  fg, getopts, hash, help, history, jobs, kill, let,
       local, logout, popd, printf, pushd, pwd, read, readonly,  return,  set,
       shift,  shopt,  source,  suspend,  test,  times,  trap,  type, typeset,
       ulimit, umask, unalias, unset,  wait  -  bash  built-in  commands,  see
       bash(1)

BASH BUILTIN COMMANDS
       Unless otherwise noted, each builtin command documented in this section as accepting options
       preceded by - accepts -- to signify the end of the options.   For  example,  the  :, true, false, and test
       builtins do not accept options.
              : [arguments]
              No effect; the command does nothing beyond  expanding  arguments
              and  performing any specified redirections.  A zero exit code is
              returned.
           .  filename [arguments]
               source filename [arguments]
              Read and execute commands from filename  in  the  current  shell

7).clear
NAME
       clear - clear the terminal screen
SYNOPSIS
       clear
DESCRIPTION
Clear clears your screen if this is possible.  It looks in the environment for the terminal type and then in the terminfo database to figure out how to clear the screen. Clear ignores any command-line parameters that may be present.

8). CP
NAME
       cp - copy files and directories
SYNOPSIS
       cp [OPTION]... [-T] SOURCE DEST
       cp [OPTION]... SOURCE... DIRECTORY
       cp [OPTION]... -t DIRECTORY SOURCE...
DESCRIPTION
       Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.
       -a, --archive
              same as -dpR
       --backup[=CONTROL]
              make a backup of each existing destination file
       -b     like --backup but does not accept an argument

9).CAL
NAME
     cal - displays a calendar
SYNOPSIS
     cal [-smjy13] [[month] year]
DESCRIPTION
 Cal displays a simple calendar.  If arguments are not specified, the current month is displayed.  The options are as follows:

     -1      Display single month output.  (This is the default.)
     -3      Display prev/current/next month output.
     -s      Display Sunday as the first day of the week.  (This is the default.)
   -m      Display Monday as the first day of the week.
     -j      Display Julian dates (days one-based, numbered from January 1).
     -y      Display a calendar for the current year.

10). history
BASH_BUILTINS(1)                                             
NAME
 bash,  :,  ., [, alias, bg, bind, break, builtin, cd, command, compgen, complete, continue, declare, dirs, disown, echo,  enable,  eval,  exec, exit,  export,  fc,  fg, getopts, hash, help, history, jobs, kill, let, local, logout, popd, printf, pushd, pwd, read, readonly,  return,  set, shift,  shopt,  source,  suspend,  test,  times,  trap,  type, typeset, ulimit , umask , unalias, unset,  wait  -  bash  built-in  commands.
     
11).CHMOD
NAME
       chmod - change file access permissions
SYNOPSIS
       chmod [OPTION]... MODE[,MODE]... FILE...
       chmod [OPTION]... OCTAL-MODE FILE...
       chmod [OPTION]... --reference=RFILE FILE...

DESCRIPTION
 This manual page documents the GNU version of chmod.  chmod changes the permissions of each given file according to mode, which can be either a symbolic  representation  of changes to make,or an octal number representing the bit pattern for the new permissions. A combination of the letters 'ugoa' controls which users' access to the file  will  be  changed:  the user who owns it (u), other users in the file's group (g), other users not in the file's group (o), or all users(a).If  none of these are given, the effect is as if 'a' were given.

12).umask
BASH_BUILTINS(1)                                             
NAME
 bash,  :,  ., [, alias, bg, bind, break, builtin, cd, command, compgen, complete, continue, declare, dirs, disown, echo,  enable,  eval,  exec, exit,  export,  fc,  fg, getopts, hash, help, history, jobs, kill, let, local, logout, popd, printf, pushd, pwd, read, readonly,  return,  set,shift,  shopt,  source,  suspend,  test,  times,  trap,  type, typeset, ulimit, umask, unalias, unset,  wait  -  bash  built-in  commands.
      
13).HEAD
NAME
       head - output the first part of files

SYNOPSIS
       head [OPTION]... [FILE]...

DESCRIPTION
       Print  the  first  10 lines of each FILE to standard output.  With more than one FILE, precede each
       with a header giving the file  name.   With no FILE, or when FILE is -, read standard input.
       -c, --bytes=[-]N
              print the first N bytes of each  file;  with  the  leading  '-',print all but the last N bytes of each file
       -n, --lines=[-]N
              print  the first N lines instead of the first 10; with the leading '-', print all but the last N lines of each file

14).TAIL
NAME
       tail - output the last part of files
SYNOPSIS
       tail [OPTION]... [FILE]...

DESCRIPTION
       Print  the  last  10  lines of each FILE to standard output.  With more than one FILE, precede each
       with a header giving the file  name.   With no FILE, or when FILE is -, read standard input.
    --retry
              keep trying to open a file even if it is inaccessible when  tail starts  or if it becomes inaccessible
              later; useful when following by name, i.e., with --follow=name
   -c, --bytes=N
              output the last N bytes

15).DATE
NAME
       date - print or set the system date and time
SYNOPSIS
       date [OPTION]... [+FORMAT]
       date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]
DESCRIPTION
       Display the current time in the given FORMAT, or set the system date.
       -d, --date=STRING
              display time described by STRING, not 'now'
       -f, --file=DATEFILE
              like --date once for each line of DATEFILE
       -r, --reference=FILE
              display the last modification time of FILE
       -R, --rfc-2822
              output date and time in RFC 2822 format

16).EXPR
NAME
       expr - evaluate expressions
SYNOPSIS
       expr EXPRESSION
       expr OPTION

DESCRIPTION
       --version
              output version information and exit
Print the value of EXPRESSION to standard output.  A blank line below separates increasing precedence groups.  EXPRESSION may be:
       ARG1 | ARG2
              ARG1 if it is neither null nor 0, otherwise ARG2
       ARG1 & ARG2
              ARG1 if neither argument is null or 0, otherwise 0

17).WHO
NAME
       who - show who is logged on
SYNOPSIS
       who [OPTION]... [ FILE | ARG1 ARG2 ]

DESCRIPTION
       -a, --all
              same as -b -d --login -p -r -t -T -u
       -b, --boot
              time of last system boot
       -d, --dead
              print dead processes
       -H, --heading
              print line of column headings
       -l, --login
              print system login processes

18).UNAME
NAME
       uname - print system information
SYNOPSIS
       uname [OPTION]...
DESCRIPTION
       Print certain system information.  With no OPTION, same as -s.
       -a, --all
              print  all  information,  in the following order, except omit -p
              and -i if unknown:
       -s, --kernel-name
              print the kernel name
       -n, --nodename
              print the network node hostname
       -r, --kernel-release
19).FINGER                (BSD General Commands Manual  )             
NAME
     finger - user information lookup program
SYNOPSIS
     finger [-lmsp] [user ...] [user@host ...]
DESCRIPTION
     The finger displays information about the system users.
     Options are:
     -s    Finger displays the user's login name, real name, terminal name and write status(as a ''*'' after the
           terminal name if write permission is denied), idle time, login time, office location and office phone number.
Login time is displayed as month, day, hours and minutes, unless more than six months ago, in which case the year is displayed rather than the hours and minutes. Unknown devices as well as nonexistent idle and login times are displayed as single asterisks.
                  
20).CMP
NAME
     cmp - compare two files
SYNOPSIS
     cmp [-l | -s] file1 file2 [skip1 [skip2]]
DESCRIPTION
The cmp utility compares two files of any type and writes the results to the standard output.  By default,
cmp is silent if the files are the same; if they differ, the byte and line number at which the first
difference occurred is reported.

     Bytes and lines are numbered beginning with one.
     The following options are available:
     -l    Print the byte number (decimal) and the differing byte values(octal) for each difference.
    -s    Print nothing for differing files; return exit status only.    
21).COMM
NAME
       comm - compare two sorted files line by line
SYNOPSIS
       comm [OPTION]... FILE1 FILE2
DESCRIPTION
Compare sorted files FILE1 and FILE2 line by line. With no options, produce three-column output. Column one contains lines unique to FILE1, column two contains lines unique to FILE2, and column three contains lines common to both files.
       -1     suppress lines unique to FILE1
       -2     suppress lines unique to FILE2
       -3     suppress lines that appear in both files

22).SORT
NAME
       sort - sort lines of text files
SYNOPSIS
       sort [OPTION]... [FILE]...
DESCRIPTION
       Write sorted concatenation of all FILE(s) to standard output.
       -b, --ignore-leading-blanks
              ignore leading blanks
       -d, --dictionary-order
              consider only blanks and alphanumeric characters
       -f, --ignore-case
              fold lower case to upper case characters
       -g, --general-numeric-sort

23).WC
NAME
       wc - print the number of newlines, words, and bytes in files
SYNOPSIS
       wc [OPTION]... [FILE]...
DESCRIPTION
Print newline, word, and byte counts for each FILE, and a total line ifmore than one FILE is specified.  With no FILE, or when FILE is -, read standard input.
       -c, --bytes
              print the byte counts
       -m, --chars
              print the character counts
       -l, --lines
              print the newline counts
       -L, --max-line-length
              print the length of the longest line

24).TTY
NAME
       tty - print the file name of the terminal connected to standard input
SYNOPSIS
       tty [OPTION]...
DESCRIPTION
       Print the file name of the terminal connected to standard input.
       -s, --silent, --quiet
              print nothing, only return an exit status
  

25).ECHO
NAME
       echo - display a line of text
SYNOPSIS
       echo [OPTION]... [STRING]...
DESCRIPTION
       Echo the STRING(s) to standard output.
       -n     do not output the trailing newline
       -e     enable interpretation of backslash escapes
       -E     disable interpretation of backslash escapes (default)
  
26).man
NAME
       man - format and display the on-line manual pages
SYNOPSIS
 man [--path]  [-m system] [-p string] [-C config_file] [-M pathlist] [-P pager] [-B browser] [-H htmlpager] [-S section_ list][section] name ...
DESCRIPTION
man formats and displays the on-line manual pages.  If you specify section, man only looks in that section of the                                                                                                                                                     manual.  name  is normally the name of the manual page, which is typically the name of a command,  function, or file.
 OPTIONS
       -C  config_file

27).MORE
NAME
     more - file perusal filter for crt viewing
DESCRIPTION
     More is a filter for paging through text one screen at a time.  This version is especially primitive. 
     Users should realize that less provides more emulation and extensive enhancements.

28).PASSWD
NAME
       passwd - update a user's authentication tokens(s)
SYNOPSIS
       passwd [-k] [-l] [-u [-f]] [-d] [-n mindays] [-x maxdays] [-w warndays] [username]
DESCRIPTION
       Passwd is used to update a user's authentication token(s). Passwd is configured to work through the
       Linux-PAM  API.   Essentially, it initializes itself as a "passwd" service with Linux-PAM and utilizes
       configured password modules to authenticate and then  update  a  user's password.

29).PWD
NAME
       pwd - print name of current/working directory
SYNOPSIS
       pwd [OPTION]
DESCRIPTION
       Print the full filename of the current working directory.
            
30).GREP                                                         
NAME
       grep, egrep, fgrep - print lines matching a pattern
SYNOPSIS
       grep [options] PATTERN [FILE...]
       grep [options] [-e PATTERN | -f FILE] [FILE...]
DESCRIPTION
       Grep  searches the named input FILEs (or standard input if no files are named, or the file name - is given)
       for lines containing a match to the given PATTERN.  By default, grep prints the matching lines. In addition,two
       variant programs egrep and fgrep are available.  Egrep is the same as grep -E. Fgrep is the same as grep -F.
 OPTIONS
       -A NUM, --after-context=NUM
              Print NUM  lines  of  trailing  context  after  matching  lines.
              Places  a  line  containing  --  between  contiguous  groups  of matches.

31).PS
NAME
ps - report a snapshot of the current processes.
SYNOPSIS
ps [options]
DESCRIPTION
ps displays information about a selection of the active processes. If you want a repetitive update of the selection
and the displayed information, use top instead.

32).RM
NAME
       rm - remove files or directories
SYNOPSIS
       rm [OPTION]... FILE...
DESCRIPTION
       This  manual  page  documents  the  GNU version of rm.  rm removes each specified file.  By default,it does not
       remove directories. If a file is unwritable, the standard input is a tty.
       --force  option is not given, rm prompts the user for whether to remove the file.  If the response is affirmative,
       the file is skipped.
OPTIONS
       Remove (unlink) the FILE(s).
       -d, --directory
              unlink FILE, even if it is  a  non-empty  directory 
           
33).set
BASH_BUILTINS(1)                                             
NAME
 bash,  :,  ., [, alias, bg, bind, break, builtin, cd, command, compgen, complete, continue, declare, dirs, disown, echo,  enable,  eval,  exec, exit,  export,  fc,  fg, getopts, hash, help, history, jobs, kill, let, local, logout, popd, printf, pushd, pwd, read, readonly,  return,  set, shift,  shopt,  source,  suspend,  test,  times,  trap,  type, typeset, ulimit, umask, unalias, unset,  wait  -  bash  built-in  commands.
      
 34).CUT
NAME
       cut - remove sections from each line of files
SYNOPSIS
       cut [OPTION]... [FILE]...
DESCRIPTION
       Print selected parts of lines from each FILE to standard output.
       -b, --bytes=LIST
              select only these bytes
       -c, --characters=LIST
              select only these characters
       -d, --delimiter=DELIM
              use DELIM instead of TAB for field delimiter
       -f, --fields=LIST


35).Read
BASH_BUILTINS(1)                                             
NAME
 bash,  :,  ., [, alias, bg, bind, break, builtin, cd, command, compgen, complete, continue, declare, dirs, disown, echo,  enable,  eval,  exec, exit,  export,  fc,  fg, getopts, hash, help, history, jobs, kill, let,local, logout, popd, printf, pushd, pwd, read, readonly,  return,  set,shift,  shopt,  source,  suspend,  test,  times,  trap,  type, typeset, ulimit, umask, unalias, unset,  wait  -  bash  built-in  commands. 
   
36). jobs
BASH_BUILTINS(1)                                            
NAME
 bash,  :,  ., [, alias, bg, bind, break, builtin, cd, command, compgen, complete, continue, declare, dirs, disown, echo,  enable,  eval, exec, exit,  export,  fc,  fg, getopts, hash, help, history, jobs, kill, let, local, logout, popd, printf, pushd, pwd, read, readonly,  return,  set, shift,  shopt,  source,  suspend,  test,  times,  trap,  type, typeset, ulimit, umask, unalias, unset,  wait  -  bash  built-in  commands.

 37).GAWK
NAME
       gawk - pattern scanning and processing language
SYNOPSIS
       gawk [ POSIX or GNU style options ] -f program-file [ -- ] file ...
       gawk [ POSIX or GNU style options ] [ -- ] program-text file ...
       pgawk [ POSIX or GNU style options ] -f program-file [ -- ] file ...
       pgawk [ POSIX or GNU style options ] [ -- ] program-text file ...

DESCRIPTION
 Gawk  is  the  GNU Project's implementation of the AWK programming language.  It conforms to the definition of  the  language  in the  POSIX1003.2  Command  Language And Utilities Standard. Pgawk is the profiling version of gawk.  It is identical in every way to gawk, except that programs run more slowly, and it automatically


38).LN
NAME
       ln - make links between files
SYNOPSIS
       ln [OPTION]... [-T] TARGET LINK_NAME   (1st form)
       ln [OPTION]... TARGET                  (2nd form)
       ln [OPTION]... TARGET... DIRECTORY     (3rd form)
       ln [OPTION]... -t DIRECTORY TARGET...  (4th form)
DESCRIPTION
       In the 1st form, create a link to TARGET with the name LINK_NAME.  In the 2nd form, create a link to TARGET in
       the current directory.  In the3rd and 4th forms, create links to each TARGET in DIRECTORY. Create hard links
       by default, symbolic links with --symbolic.   When creating hard links, each TARGET must exist.
       --backup[=CONTROL]             
                                make a backup of each existing destination file

39).ENV
NAME
       env - run a program in a modified environment
SYNOPSIS
       env [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]
DESCRIPTION
       Set each NAME to VALUE in the environment and run COMMAND.

       -i, --ignore-environment
              start with an empty environment
       -u, --unset=NAME
              remove variable from the environment
40).KILL
NAME
       kill - terminate a process
SYNOPSIS
       kill [ -s signal | -p ] [ -a ] pid ...
       kill -l [ signal ]
DESCRIPTION
       The command kill sends the specified signal to the specified process or process group.  If no signal is specified,
       the  TERM  signal  is  sent. The  TERM  signal  will  kill processes which do not catch this signal.
 OPTIONS
       pid... Specify the list of processes that kill should signal. 
             
41).alias
BASH_BUILTINS(1)                                             
NAME
 bash,  :,  ., [, alias, bg, bind, break, builtin, cd, command, compgen, complete, continue, declare, dirs, disown, echo,  enable,  eval,  exec, exit,  export,  fc,  fg, getopts, hash, help, history, jobs, kill, let, local, logout, popd, printf, pushd, pwd, read, readonly,  return,  set, shift,  shopt,  source,  suspend,  test,  times,  trap,  type, typeset, ulimit, umask, unalias, unset,  wait  -  bash  built-in  commands.

42).DIFF
NAME
       diff - find differences between two files
SYNOPSIS
       diff [options] from-file to-file
DESCRIPTION
       In the simplest case, diff compares the contents of the two files from file and to-file.  A file name of – stands for
       text read from the standard  input.   As  a special case, diff - - compares a copy of standard input to itself.
                        
43).locate                                                            
NAME
       locate - find files by name
SYNOPSIS
       locate [OPTION]... PATTERN...
DESCRIPTION
       locate  reads  one or more databases prepared by updatedb(8) and writes file names matching at least
       one of the PATTERNs  to  standard  output, one per line.
      PATTERNs  can contains globbing characters.  If any PATTERN contains no globbing characters, locate behaves as
  if the pattern were *PATTERN*. By default, locate does not check whether files found in database still exist; 
      locate  can  never  report  files created after the most recent update of the relevant database.
      
44).FIND
NAME
       find - search for files in a directory hierarchy
SYNOPSIS
       find [-H] [-L] [-P] [path...] [expression]
DESCRIPTION
       This  manual page documents the GNU version of find.  GNU find searches the directory tree rooted at
       each given file  name  by  evaluating  the given  expression  from left to right, according to the rules of
       precedence , until the outcome  is  known at which point find moves on to the next file name.
                
45).INFO
NAME
       info - read Info documents
SYNOPSIS
       info [OPTION]... [MENU-ITEM...]
DESCRIPTION
       Read documentation in Info format.
OPTIONS
       --apropos=STRING
              look up STRING in all indices of all manuals.
       -d, --directory=DIR
              add DIR to INFOPATH.
       --dribble=FILENAME
              remember user keystrokes in FILENAME.
       -f, --file=FILENAME
              specify Info file to visit.


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