using awk iteratively in a script to assign variable values


 
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# 1  
Old 11-02-2011
using awk iteratively in a script to assign variable values

I have a log file that has certain fields that I want to evaluate, and depending on the value in those fields, I want to put the value of a different field in that line in a particular variable that I'll use later on down the log file. Sort of like setting a switch to change what I do with a bunch of lines I've been saving as I go through the log. The log file looks something like this:

Code:
blah blah blah 23
blah blah blah 45
blah blah start 33
blah blah blah 93
blah blah blah 11
.
.
.
[unpredictable number of lines]
.
.
.
blah blah blah 88
blah blah bad_trial 67
[etc.]

I want to put all the lines between the line that has "start" and the line that has "bad_trial" into a new text file, with each line stripping out everything but the first entry ("blah") and the number, e.g. the new file will look like:

Code:
blah 93
blah 11
.
.
.
blah 88

[followed by other sets of lines between "start" and "bad_trial" lines].

Ultimately I want to append these lines to another file, for later evaluation in a different program.

I've gotten so far as to have the script read in the file line by line and use awk to check for values in each line, and if it finds them, put the number in a variable (that I was going to use to write out to a new file). But when I have it put things in a variable, it seems to just keep adding values to the end of the existing values in that variable, rather than replacing the existing value. Here is what I have:

Code:
while read line; do trial_type=`awk '$3 =="bad_trial" { print $4 }'` ; echo $trial_type; done < lamar-Training_5seq.log

(I know this doesn't do what my ultimate goal is, I'm just trying to get there in baby steps)

The value of $trial_type at the end of this is a string of numbers separated by spaces, in which the numbers are the values in the 4th field for all the lines that have "bad_trial" in them. What I want to have happen in this simple script instead is to replace the value of $trial_type, not append it to the existing value of $trial_type.

Any ideas for what I'm doing wrong, and/or suggestions for how to get to my ultimate goal, please let me know! And thanks for reading this far.

-Tom

Moderator's Comments:
Mod Comment Use code tags please, got a PM. Can also open this post in edit mode and see what tags I inserted, thanks.

Last edited by zaxxon; 11-02-2011 at 05:49 AM.. Reason: code tags, see PM
# 2  
Old 11-02-2011
It's probably easier to just do the whole thing in awk. Something like:
Code:
awk "BEGIN {inside=0} $3 ~ /start/ {inside=1} $3 ~ /bad_trial/ {inside=0} {if (inside==1) {print $1 FS $4}" lamar-Training_5seq.log

(untested!)
# 3  
Old 11-02-2011
thanks for that suggestion!

When I try that, I get errors:


Code:
awk "BEGIN {inside=0} $3 ~ /start/ {inside=1} $3 ~ /bad_trial/ {inside=0} {if (inside==1) {print $1 FS $4}" lamar-Training_5seq.log
awk: syntax error at source line 1
 context is
	BEGIN {inside=0}  >>>  ~ <<< 
	missing }
awk: bailing out at source line 1

What is wrong here?
# 4  
Old 11-02-2011
a variation on the theme:
Code:

awk '$3 ~ /start/ {in++;next} $3 ~ /bad_trial/ {in=0;next} in{print $1 FS $NF}" lamar-Training_5seq.log

use 'nawk' if on Solaris.
# 5  
Old 11-02-2011
I had to change the " to a ' to get it to run (was that a mistake on my part?), but I now get:

Code:
awk '$4 ~ /start/ {in++;next} $4 ~ /bad_trial/ {in=0;next} in{print $1 FS $NF}' lamar-Training_5seq.log
awk: syntax error at source line 1
 context is
	$4 ~ /start/ >>>  {in <<< ++;next} $4 ~ /bad_trial/ {in=0;next} in{print $1 FS $NF}
awk: illegal statement at source line 1

---------- Post updated at 05:44 PM ---------- Previous update was at 05:44 PM ----------

I don't have nawk...
# 6  
Old 11-02-2011
sorry, 'in' is reserved.
Code:

awk '$3 ~ /start/ {i++;next} $3 ~ /bad_trial/ {i=0;next} i{print $1 FS $NF}' lamar-Training_5seq.log

 
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