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Full Discussion: grep vs do while read
Top Forums Shell Programming and Scripting grep vs do while read Post 302281777 by 15a0 on Thursday 29th of January 2009 12:01:12 PM
Old 01-29-2009
grep vs do while read
I have inherited the UNIX scripting duties for our team and have only been at this for a few months so I apologize for what may be a simple question.

We have a script we are reworking. Part of this script takes a parameter and reads a csv file. When it finds a matching line, the cut command is used to parse out and assign script variables from the matching line.

This works fine (code shown below). My question is really just a general one. I get the idea of using grep to "filter" just the records we want (based on $1, and then again, the lines that end with 'C')

In our case the file is very small no more than 25 lines. I am wondering if we could also use a do while read loop to actually "read" the file line by line instead of using grep - what would be the merits of each approach?

Any input you have would be greatly appreciated!

thanks,

JH




set RECORDS = `grep ^$1 ${CFGFILE} | grep 'C$'`

foreach record ( ${RECORDS} )
set rSID = `echo $record | tr -s " " | cut -f1 -d","`
set rCLIENT = `echo $record | tr -s " " | cut f2 -d","'
set rINSTANCE = `echo $record | tr -s " " | cut -f3 -d","`
set rSERVER = `echo $record | tr -s " " | cut -f4 -d","`
set rTYPE = `echo $record | tr -s " " | cut -f5 -d","`
 

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LEARN ABOUT REDHAT

cut

CUT(1)									FSF								    CUT(1)

NAME

       cut - remove sections from each line of files

SYNOPSIS

       cut [OPTION]... [FILE]...

DESCRIPTION

       Print selected parts of lines from each FILE to standard output.

       Mandatory arguments to long options are mandatory for short options too.

       -b, --bytes=LIST
	      output only these bytes

       -c, --characters=LIST
	      output only these characters

       -d, --delimiter=DELIM
	      use DELIM instead of TAB for field delimiter

       -f, --fields=LIST
	      output only these fields;  also print any line that contains no delimiter character, unless the -s option is specified

       -n     with -b: don't split multibyte characters

       -s, --only-delimited
	      do not print lines not containing delimiters

       --output-delimiter=STRING
	      use STRING as the output delimiter the default is to use the input delimiter

       --help display this help and exit

       --version
	      output version information and exit

       Use one, and only one of -b, -c or -f.  Each LIST is made up of one range, or many ranges separated by commas.  Each range is one of:

       N      N'th byte, character or field, counted from 1

       N-     from N'th byte, character or field, to end of line

       N-M    from N'th to M'th (included) byte, character or field

       -M     from first to M'th (included) byte, character or field

       With no FILE, or when FILE is -, read standard input.

AUTHOR

       Written by David Ihnat, David MacKenzie, and Jim Meyering.

REPORTING BUGS

       Report bugs to <bug-coreutils@gnu.org>.

COPYRIGHT

       Copyright (C) 2002 Free Software Foundation, Inc.
       This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
       LAR PURPOSE.

SEE ALSO

       The full documentation for cut is maintained as a Texinfo manual.  If the info and cut programs are properly installed at  your	site,  the
       command

	      info cut

       should give you access to the complete manual.

cut (coreutils) 4.5.3						   February 2003							    CUT(1)
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