Question

awk/grep question

Asked by: kkatula

I have a Unix script that I need to parse a data file and kick out any line where the 4th field has less than 15 characters. I have this which works fine until there are no lines that need to be kicked out.  When every line has a field 4 with at least 15 characters, the grep below yields a zero byte file.  Any ideas?

awk -F"|", 'length($4)<15' /tmp/listfinal >> /tmp/deleteme
/usr/xpg4/bin/grep -v -f /tmp/deleteme /tmp/listfinal > /tmp/listclean

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Asked On
2009-10-22 at 07:27:55ID24834641
Topics

Shell Scripting

,

Bourne Shell (sh)

,

Unix Systems Programming

Participating Experts
2
Points
500
Comments
2

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Answers

 

by: amit_gPosted on 2009-10-22 at 08:18:31ID: 25635220

Check the contents of /tmp/deleteme. If it has a newline (empty visually), it would cause the issue that you are reporting. This method that you are using is not reliable anyway. If a line is added to /tmp/deleteme, it may cause a valid line from /tmp/listfinal to be deleted if that line is a substring in any valid line. For example, take a case of just two field file and assume this is added as an invalid line in  /tmp/deleteme

Hello|there

/usr/xpg4/bin/grep -v -f /tmp/deleteme /tmp/listfinal

would cause all of the following lines from /tmp/listfinal to be deleted even though they may be valid

Hello|there
Hello|thereIam
Hello|there Iam

If your files are small you can run awk twice.

awk -F"|" 'length($4)<15' /tmp/listfinal >> /tmp/deleteme
awk -F"|" 'length($4)>=15' /tmp/listfinal >> /tmp/listclean

If not, you can use the method given in one of your previous question. Something like it

awk -F, '$5 != "" {print > "/tmp/list.clean"} $5 == "" {print > "/tmp/deleteme"};' /tmp/list && mv /tmp/list.clean /tmp/list

 

by: oheilPosted on 2009-10-22 at 08:52:56ID: 25635642

my approach:

awk 'BEGIN{FS="|"}{if(length($4)>=15){print $0}}' /tmp/listfinal

If there are lines without a 4th column and you want them too:

awk 'BEGIN{FS="|"}{if(NF<4||length($4)>=15){print $0}}' /tmp/listfinal

No need for grep.

Regards,

Oli

20120131-EE-VQP-002

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