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Full Discussion: Using awk to read a specific line and a specific field on that line.
Top Forums Shell Programming and Scripting Using awk to read a specific line and a specific field on that line. Post 302543390 by agama on Sunday 31st of July 2011 01:13:43 PM
Old 07-31-2011
Quote:
Originally Posted by Bungkai

Code:
sed -i "s/$searchName\ $2/$name\ $lname/g" database.txt

This works for me assuming that searchName == John, $2 == Wall. If you've invoked your script with just John on the command line, $2 will be null, then you'll end up with the results that you posted. The small script I wrote to test your code includes some error checking that might be beneficial in your case so I've posted it as an example.

Code:
#!/usr/bin/env ksh

if [[ $# != 4 ]]
then
   echo "error: missing parms. expected:  name lastname newname new-lastname"
   exit 1
fi
searchName=$1
# $2 is not assigned and used directly later 
name=$3
lname=$4

sed  "s/$searchName\ $2/$name\ $lname/g" test.data

I would recommend assigning $2 to a named variable; while it is fine the way it is, it makes your script easier to read if it were something like this:

Code:
sed  "s/$searchName\ $searchLastname/$name\ $lname/g" test.data

I also don't believe that you need to escape the spaces. This should work:
Code:
sed  "s/$searchName $2/$name $lname/g" test.data

and again makes the code easier to read.

---------- Post updated at 13:13 ---------- Previous update was at 13:10 ----------

Thought I would also note that I dropped the -i from my testing because the version of sed that I prefer does not implement it. It should work just fine if you prefer to use that option.
 

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LEARN ABOUT BSD

join

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 specified 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.

7th Edition							  April 29, 1985							   JOIN(1)
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