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Top Forums Shell Programming and Scripting How to create file and file content based existing information? Post 302994030 by Torhong on Friday 17th of March 2017 03:40:52 PM
Old 03-17-2017
Quote:
Originally Posted by RudiC
With just glance at your script I see that
- both input files being read via what seems to be the same file descriptor - might work by accident but is sloppy programming; use different fd explicitly
- if it would work, for every line in file1 the entire file2 is being read - highly inefficient
- every time fname is found in the input files, its hitherto existing contents will be overwritten - mayhap undesired
Thanks RudiC.

you are right, the second loop is very inefficient. is there any way to fix it without using awk as I am not familiar with awk.

thanks
 

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JOIN(1) 						      General Commands Manual							   JOIN(1)

NAME
join - relational database operator SYNOPSIS
join [ options ] file1 file2 DESCRIPTION
Join forms, on the standard output, a join of the two relations specified by the lines of file1 and file2. If file1 is `-', the standard input is used. File1 and file2 must be sorted in increasing ASCII collating sequence on the fields on which they are to be joined, normally the first in each line. There is one line in the output for each pair of lines in file1 and file2 that have identical join fields. The output line normally con- sists of the common field, then the rest of the line from file1, then the rest of the line from file2. Fields are normally separated by blank, tab or newline. In this case, multiple separators count as one, and leading separators are dis- carded. These options are recognized: -an In addition to the normal output, produce a line for each unpairable line in file n, where n is 1 or 2. -e s Replace empty output fields by string s. -jn m Join on the mth field of file n. If n is missing, use the mth field in each file. -o list Each output line comprises the fields specifed in list, each element of which has the form n.m, where n is a file number and m is a field number. -tc Use character c as a separator (tab character). Every appearance of c in a line is significant. SEE ALSO
sort(1), comm(1), awk(1) BUGS
With default field separation, the collating sequence is that of sort -b; with -t, the sequence is that of a plain sort. The conventions of join, sort, comm, uniq, look and awk(1) are wildly incongruous. JOIN(1)
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