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Top Forums Shell Programming and Scripting Script Optimization - large delimited file, for loop with many greps Post 302516128 by Corona688 on Thursday 21st of April 2011 05:10:45 PM
Old 04-21-2011
foo | grep | cut | sed | really | long | pipe | chain is never efficient, and you're doing this on almost every line. You've also got a lot of useless use of backticks, and useless use of cat. Whenever you have 'for file in `cat foo` you could've done
Code:
while read file
do
...
done < foo

much more efficiently. You can also do
Code:
 while stuff ; do ... ; done 2>filename

to redirect stderr once for the whole loop instead of doing a special redirection for each and every individual command.

You can also set LC_ALL once instead of doing so for each and every individual command.

In your defense, you've been forced to deal with input data that looks like line noise! Smilie I don't entirely understand what you're doing. Why are you csplitting on 10000 and /^ST/ ? Are two non-word characters in a row, **, supposed to imply a blank record between them? Finally, what is your system, what is your shell? That will have a big effect on the tools available to you.

I've started writing a solution in awk.

Last edited by Corona688; 04-21-2011 at 06:27 PM..
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SCRIPT(1)						    BSD General Commands Manual 						 SCRIPT(1)

NAME
script -- make typescript of terminal session SYNOPSIS
script [-a] [-f] [-q] [-t] [file] DESCRIPTION
Script makes a typescript of everything printed on your terminal. It is useful for students who need a hardcopy record of an interactive session as proof of an assignment, as the typescript file can be printed out later with lpr(1). If the argument file is given, script saves all dialogue in file. If no file name is given, the typescript is saved in the file typescript. Options: -a Append the output to file or typescript, retaining the prior contents. -f Flush output after each write. This is nice for telecooperation: One person does `mkfifo foo; script -f foo' and another can super- vise real-time what is being done using `cat foo'. -q Be quiet. -t Output timeing data to standard error. This data contains two fields, separated by a space. The first field indicates how much time elapsed since the previous output. The second field indicates how many characters were output this time. This information can be used to replay typescripts with realistic typing and output delays. The script ends when the forked shell exits (a control-D to exit the Bourne shell (sh(1)), and exit, logout or control-d (if ignoreeof is not set) for the C-shell, csh(1)). Certain interactive commands, such as vi(1), create garbage in the typescript file. Script works best with commands that do not manipulate the screen, the results are meant to emulate a hardcopy terminal. ENVIRONMENT
The following environment variable is utilized by script: SHELL If the variable SHELL exists, the shell forked by script will be that shell. If SHELL is not set, the Bourne shell is assumed. (Most shells set this variable automatically). SEE ALSO
csh(1) (for the history mechanism), replay(1). HISTORY
The script command appeared in 3.0BSD. BUGS
Script places everything in the log file, including linefeeds and backspaces. This is not what the naive user expects. Linux July 30, 2000 Linux
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