Cat (Bash)

cat: Concatenate files and send to standard output.

$ man cat

CAT(1)                                             User Commands                                             CAT(1)

NAME
       cat - concatenate files and print on the standard output

SYNOPSIS
       cat [OPTION]... [FILE]...

DESCRIPTION
       Concatenate FILE(s) to standard output.

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

       -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

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.

COPYRIGHT
       Copyright   ©   2018   Free  Software  Foundation,  Inc.   License  GPLv3+:  GNU  GPL  version  3  or  later
       <https://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent per‐
       mitted by law.

SEE ALSO
       tac(1)

       Full documentation at: <https://www.gnu.org/software/coreutils/cat>
       or available locally via: info '(coreutils) cat invocation'

GNU coreutils 8.30                                 September 2019                                            CAT(1)

I have the impression that cat is often used as a placeholder when working with streams, a bit similar to echo.

See also

• Data streams (Bash)