02-02-2018
They are only equivalent in bash, ksh93 and zsh. $(< file) is faster than $(cat file), but the latter is POSIX compliant whereas the former is not.
Last edited by Scrutinizer; 02-03-2018 at 01:44 AM..
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cat(1) General Commands Manual cat(1)
Name
cat - concatenate and print data
Syntax
cat [ -b ] [ -e ] [ -n ] [ -s ] [ -t ] [ -u ] [ -v ] file...
Description
The command reads each file in sequence and displays it on the standard output. Therefore, to display the file on the standard output you
type:
cat file
To concatenate two files and place the result on the third you type:
cat file1 file2 > file3
To concatenate two files and append them to a third you type:
cat file1 file2 >> file3
If no input file is given, or if a minus sign (-) is encountered as an argument, reads from the standard input file. Output is buffered in
1024-byte blocks unless the standard output is a terminal, in which case it is line buffered. The utility supports the processing of 8-bit
characters.
Options
-b Ignores blank lines and precedes each output line with its line number.
-e Displays a dollar sign ($) at the end of each output line.
-n Precedes all output lines (including blank lines) with line numbers.
-s Squeezes adjacent blank lines from output and single spaces output.
-t Displays non-printing characters (including tabs) in output. In addition to those representations used with the -v option, all tab
characters are displayed as ^I.
-u Unbuffers output.
-v Displays non-printing characters (excluding tabs and newline) as the ^x. If the character is in the range octal 0177 to octal 0241,
it is displayed as M-x. The delete character (octal 0177) displays as ^?. For example, is displayed as ^X.
See Also
cp(1), ex(1), more(1), pr(1), tail(1)
cat(1)