Package: moreutils
Version: 0.22
Severity: important
% man sponge | grep DESC -nA 4
11:DESCRIPTION
12- sponge reads standard input and writes it out to the specified
file.
13- Unlike a shell redirect, sponge soaks up all its input before
opening
14- the output file. This allows for constructing pipelines that
read from
15- and write to the same file.
Let's try such a pipeline, here's the before 'sponge' version, with
separate input and output files:
% F=/tmp/nums ; seq 1 100000 > $F ; wc $F ; cat $F | sort > ${F}2 ; wc ${F}2
100000 100000 588895 /tmp/nums
100000 100000 588895 /tmp/nums2
And 2 different 'sponge' versions, (with and without 'cat'), with
a pipeline that reads and writes from and to the same file:
% F=/tmp/nums ; seq 1 100000 > $F ; wc $F ; sponge < $F | sort > $F ; wc $F
100000 100000 588895 /tmp/nums
0 0 0 /tmp/nums
% F=/tmp/nums ; seq 1 100000 > $F ; wc $F ; cat $F | sponge | sort > $F ;
wc $F100000 100000 588895 /tmp/nums
0 0 0 /tmp/nums
Last, the 'cat' version, without 'sponge'
% F=/tmp/nums ; seq 1 100000 > $F ; wc $F ; cat $F | sort > $F ; wc $F
100000 100000 588895 /tmp/nums
0 0 0 /tmp/nums
As can be seen, 'sponge' has the same effect as no 'sponge'.
Hope this helps...
-- System Information:
Debian Release: lenny/sid
APT prefers unstable
APT policy: (500, 'unstable')
Architecture: i386 (i686)
Kernel: Linux 2.6.21-1-686 (SMP w/1 CPU core)
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968) (ignored: LC_ALL set to C)
Shell: /bin/sh linked to /bin/dash
Versions of packages moreutils depends on:
ii libc6 2.6-2 GNU C Library: Shared libraries
ii perl 5.8.8-7 Larry Wall's Practical Extraction
moreutils recommends no packages.
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