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Explanation of Nawk command

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# 1  
Old 03-26-2019
Explanation of Nawk command
Hi Folks,

I am struggling to understand nawk command which was used by another developer.
Can you please explain what each character or string is doing here below:

Code:
if [ `nawk -F, 'NR==FNR {s=s sep $2; sep="|"; next} $0~s {c++} END {print c+0}' ${Error_file} ${Log_File_Name}` -gt 0 ] ; then

Last edited by Scrutinizer; 03-26-2019 at 02:15 PM.. Reason: code tags
# 2  
Old 03-26-2019
By just staring at it, I'd guess it creates an "alternation regex" from the second, comma separated field of the lines of ${Error_file}, then scans through ${Log_File_Name} if its lines match any of those, counts the matches, and finally prints the count to stdout, to be used by a "command substitution" in the shell if [ construct.
# 3  
Old 03-27-2019
Code:
{s=s sep $2; sep="|"; next} $0~s {c++} END {print c+0}

In the above, where is it mentioned that it is a 'comma' separated field.

what does 'sep' denotes here. sep="|" i was thinking that it is a pipe separator.

and what does s=s denotes here ?




Moderator's Comments:
Mod Comment Please use CODE tags as required by forum rules!
Last edited by RudiC; 03-27-2019 at 06:27 AM.. Reason: Added CODE tags.
# 4  
Old 03-27-2019
Quote:
Originally Posted by kirans.229
Code:
{s=s sep $2; sep="|"; next} $0~s {c++} END {print c+0}

In the above, where is it mentioned that it is a 'comma' separated field.
Nowhere. -F, sets the field separator.


Quote:
what does 'sep' denotes here. sep="|" i was thinking that it is a pipe separator.
That's a variable name, and yes, it's intended to be used a separator


Quote:
and what does s=s denotes here ?
It a variable assignment, but incompletely quoted. s=s sep $2 is the complete one, assigning the concatenation of s'(old) value, sep, and field two to (new) s .
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