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Top Forums Shell Programming and Scripting Reading ALL BUT the first and last line of a huge file Post 302969946 by Scrutinizer on Wednesday 30th of March 2016 01:52:00 PM
Old 03-30-2016
Tested with a 2 GB file (excluding writing to a file which should be similar for all approaches):
Code:
$ time sed '1d;$d' greptestin1 > /dev/null

real	0m29.835s
user	0m29.186s
sys	0m0.591s
$ time awk 'NR>2{print p}{p=$0}' greptestin1 > /dev/null    # BSD awk

real	1m44.183s
user	1m43.627s
sys	0m0.481s
$ time mawk 'NR>2{print p}{p=$0}' greptestin1 > /dev/null

real	0m14.982s
user	0m14.463s
sys	0m0.498s
$ time gawk 'NR>2{print p}{p=$0}' greptestin1 > /dev/null

real	0m24.682s
user	0m24.210s
sys	0m0.414s
$ time gawk4 'NR>2{print p}{p=$0}' greptestin1 > /dev/null

real	0m27.621s
user	0m27.173s
sys	0m0.419s

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rusage(1B)					     SunOS/BSD Compatibility Package Commands						rusage(1B)

NAME
rusage - print resource usage for a command SYNOPSIS
/usr/ucb/rusage command DESCRIPTION
The rusage command is similar to time(1). It runs the given command, which must be specified; that is, command is not optional as it is in the C shell's timing facility. When the command is complete, rusage displays the real (wall clock), the system CPU, and the user CPU times which elapsed during execution of the command, plus other fields in the rusage structure, all on one long line. Times are reported in sec- onds and hundredths of a second. EXAMPLES
Example 1 The format of rusage output The example below shows the format of rusage output. example% rusage wc /usr/share/man/man1/csh(1) 3045 13423 78071 /usr/share/man/man1/csh(1) 2.26 real 0.80 user 0.36 sys 11 pf 38 pr 0 sw 11 rb 0 wb 16 vcx 37 icx 24 mx 0 ix 1230 id 9 is example% Each of the fields identified corresponds to an element of the rusage structure, as described in getrusage(3C), as follows: real elapsed real time user ru_utime user time used sys ru_stime system time used pf ru_majflt page faults requiring physical I/O pr ru_minflt page faults not requiring physical I/O sw ru_nswap swaps rb ru_inblock block input operations wb ru_oublock block output operations vcx ru_nvcsw voluntary context switches icx ru_nivcsw involuntary context switches mx ru_maxrss maximum resident set size ix ru_ixrss currently 0 id ru_idrss integral resident set size is ru_isrss currently 0 ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWscpu | +-----------------------------+-----------------------------+ SEE ALSO
csh(1), time(1), getrusage(3C), attributes(5) BUGS
When the command being timed is interrupted, the timing values displayed may be inaccurate. SunOS 5.11 14 Sep 1992 rusage(1B)
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