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Full Discussion: sed performance
Top Forums UNIX for Advanced & Expert Users sed performance Post 302174556 by bakunin on Tuesday 11th of March 2008 12:04:10 PM
Old 03-11-2008
The reason is how sed works: it never changes the file it is working on, but - per default - puts it results to <stdout>. The "-i" option, as ghostdog74 has pointed out, is a non-standard extension to sed and it probably works by producing an intermediary file and then replacing the original.

So the difference between what sed has to do and grep has to do is:

Code:
grep                             sed
            read the file
         parse it/change it
output to <stdout>      output to temp file
-                       replace original file with temp file

Probably you could "even the score" by having sed put its output to <stdout> too and compare the times then or - even better, as it eliminates the output delay completely - directing both grep's and sed's output to /dev/null and compare the times then.

I hope this helps.
 

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CH_LAB(1)						    BSD General Commands Manual 						 CH_LAB(1)

NAME
ch_lab -- change/copy label files SYNOPSIS
ch_lab [-S frame spacing] [-start time] [-end time] [-ext file extension] [-extract file] [-extend time] [-f sample frequency] [-lf sample frequency] [-itype file type] [-key key file] [-lablist list of labels] [-length time] [-map map file] [-name feature name] [-class class] [-o output file] [-otype file type] [-pad high | low] [-pos list of labels] [-q timestep] [-range range] [-sed sed file] [fl shift time delta] [-style output stype] [-vocab vocab file] [-verify] [-nopath] [-base] [-combine] [-divide] [-h] input files ... DESCRIPTION
ch_lab copies from one or more input label files to an output label file, optionally performing various operations along the way. The following option flags are recognized: -h Print a summary of usage to standard output. -S frame spacing frame spacing of output -start time start time, in seconds, for label extraction -end time end time, in seconds, for label extraction -ext file extension filename extension to use for multiple output files -extract file extract a single file from a list of files -extend time extend track file by time seconds beyond label file -f sample frequency sample frequency of label file -lf sample frequency sample frequency for labels -itype file type type of input label file: esps htk ogi -key key file key label file -lablist list list of labels to be considered as blank -length time length of track produced, in seconds -map map file label mapping file -name feature name eg. Fo Phoneme -class class name of class defined in op file -o output file output file name -otype file type output file type: xmg, ascii, esps, htk -pad high | low pad with high or low values -pos list list of labels to be regarded as 'pos' -q timestep quantize label timings to nearst value -range range difference between high and low values -sed sed file perform regex editing using sed file fl shift time delta shift the times of the labels -style output style output style e.g. track -vocab file file containing list of words in vocabulary -verify check that only labels in vocab file are in label file -nopath ignore pathnames when searching label lists -base use base filenames for lists of label files -combine -divide SEE ALSO
ch_wave(1) ch_track(1) Edinburgh Speech Tools April 5, 2001 Edinburgh Speech Tools
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