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Top Forums Shell Programming and Scripting /dev/null what is the use of it? Post 302211324 by pppswing on Thursday 3rd of July 2008 05:27:47 AM
Old 07-03-2008
To empty a file.

cat /dev/null > myfileToEmpty.txt
 

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CAT(1)							      General Commands Manual							    CAT(1)

NAME
cat - catenate and print SYNOPSIS
cat [ -u ] [ -n ] [ -s ] [ -v ] file ... DESCRIPTION
Cat reads each file in sequence and displays it on the standard output. Thus cat file displays the file on the standard output, and cat file1 file2 >file3 concatenates the first two files and places the result on the third. If no input file is given, or if the argument `-' is encountered, cat reads from the standard input file. Output is buffered in the block size recommended by stat(2) unless the standard output is a terminal, when it is line buffered. The -u option makes the output completely unbuffered. The -n option displays the output lines preceded by lines numbers, numbered sequentially from 1. Specifying the -b option with the -n option omits the line numbers from blank lines. The -s option crushes out multiple adjacent empty lines so that the output is displayed single spaced. The -v option displays non-printing characters so that they are visible. Control characters print like ^X for control-x; the delete char- acter (octal 0177) prints as ^?. Non-ascii characters (with the high bit set) are printed as M- (for meta) followed by the character of the low 7 bits. A -e option may be given with the -v option, which displays a `$' character at the end of each line. Specifying the -t option with the -v option displays tab characters as ^I. SEE ALSO
cp(1), ex(1), more(1), pr(1), tail(1) BUGS
Beware of `cat a b >a' and `cat a b >b', which destroy the input files before reading them. 4th Berkeley Distribution May 5, 1986 CAT(1)
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