cat command is used to concatenate or displays the contents of a file.
To use it, type cat, and then press enter key

/home/user# cat
Hello World
Hello World

The text indicates what we typed to cat

İf you type this row and then press enter

To display the contents of a file, type

/home/user# cat filename

To see linux commands press Tab key,
If you want to learn commands beginning with c you can write c then press Tab key

Display and concatenate files.

/home/user# cat

Will read from STDIN and print to STDOT every line you enter.

/home/user# cat file1 [file2] ...

Will concatenate all files in one and print them to STDOUT

/home/user# cat > filename

Will take whatever you type from STDIN and will put it into the file filename
To exit cat or cat > filename type Ctrl+D to indicate EOF (End of File). To end many unix command, type end-of-file command (EOF) [hold down the key labeled “Ctrl” and press “d” (Ctrl+d) ]

 

Linux Cat Command Man Page

CAT(1)                           User Commands                          CAT(1)



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 nonempty output lines, overrides -n

       -e     equivalent to -vE

       -E, --show-ends
              display $ at end of each line

       -n, --number
              number all output lines

       -s, --squeeze-blank
              suppress repeated empty output lines

       -t     equivalent to -vT

       -T, --show-tabs
              display TAB characters as ^I

       -u     (ignored)

       -v, --show-nonprinting
              use ^ and M- notation, except for LFD and TAB

       --help display this help and exit

       --version
              output version information and exit

       With no FILE, or when FILE is -, read standard input.

EXAMPLES
       cat f - g
              Output f's contents, then standard input, then g's contents.

       cat    Copy standard input to standard output.

AUTHOR
       Written by Torbjorn Granlund and Richard M. Stallman.

REPORTING BUGS
       Report cat bugs to bug-coreutils@gnu.org
       GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
       General help using GNU software: <http://www.gnu.org/gethelp/>
       Report cat translation bugs to <http://translationproject.org/team/>

COPYRIGHT
       Copyright  ©  2013  Free Software Foundation, Inc.  License GPLv3+: GNU
       GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free  to  change  and  redistribute  it.
       There is NO WARRANTY, to the extent permitted by law.

SEE ALSO
       tac(1)

       The  full  documentation for cat is maintained as a Texinfo manual.  If
       the info and cat programs are properly installed at your site, the com‐
       mand

              info coreutils 'cat invocation'

       should give you access to the complete manual.



GNU coreutils 8.21                March 2014                            CAT(1)