Re: Bourn Shell Scripts that Produce Multiple Files
Mario Hoerich writes:
This sounds a bit like a truncation issue.
If you do something like
command1 bar
# some code
command2 bar
then the second redirect will truncate the file to 0 bytes
before redirecting the output from command2 into it.
Yes.
My code was very similar to what you describe only more like:
command1 bar
#some code
command2 bar2
#should leave bar alone and open bar2
#Instead, bar and bar2 both end up empty of anything.
Try using instead of , as it appends to the file.
What's sad is, I think I tried that but forgot to remove some
older versions of the same files created by a less elegant method so
it looked like the new files had too many lines in them and I figured
that appending didn't work either. I should have cleaned house first
and things would have been fine.
Appending did solve the problem.
If this doesn't help, please post the script (or a simplified
version thereof). We're not clairvoyant, you know... :)
Here is the simplified origin of the problem:
#! /bin/sh
searchfor () {
#line of awk that produces standard output
return 0
}
while read currentnumber; do
#This line does work according to your suggestion.
searchfor $currentnumber.txt
#This line was what I had which opens new files but never fills them:
#searchfor $currentnumber.txt
done ~/numbers
The value held in $currentnumber.txt changes with each loop
iteration so we should be writing to bar2, bar3, etc and leaving bar1
alone. It apparently does not work that way. It reminds me of what
happens in C if a program ends without closing an open file for
whatever reason. The buffer never gets emptied so the file is left
either empty or partially filled depending upon luck and how much data
got written to the disk before the abnormal end.
My short-term problem is solved so thanks again, but it
appears that even opening new files without appending them confuses
the shell on previously-opened files such that you do not receive any
data in any of the files.
Martin McCormick WB5AGZ Stillwater, OK
OSU Information Technology Division Network Operations Group
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Bourn Shell Scripts that Produce Multiple Files
I wrote a Bourn Shell script which has a while loop in it that reads a file line by line. The output of the script is supposed to go to a file with a different name for each iteration of the loop. This scheme is obviously a rotten idea because all the new files end up created, but quite empty. If I take out the $newfilename.txt directive, I get the proper output at stdout so the only problem is with changing the file name in the middle of the game several times. I think that either the output gets lost in buffers or I am killing the association between the file descriptor that was first opened and all the new files that get created each time the loop runs. bash doesn't have anything like a fflush(); function, does it? I even tried piping the output through cat as in |cat $newfilename.txt and even |tee $newfilename.txt which sends the output to stdout and to any files you give to tee as arguments. The results are always the same. When I used tee, I could read proper output being sent through stdout, but those files were still as blank as ever. The man page for bash doesn't even contain the word flush nor does it discuss output buffering regarding redirection or closing open files. I actually made the script work by splitting it in to two shell scripts which caused the part producing the output to exit each time. That certainly caused output to go to the proper files, but I think there should be a way to make it all happen from one script. Thank you for any suggestions. Martin McCormick WB5AGZ Stillwater, OK OSU Information Technology Division Network Operations Group ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: Bourn Shell Scripts that Produce Multiple Files
# Martin McCormick: I wrote a Bourn Shell script which has a while loop in it that reads a file line by line. The output of the script is supposed to go to a file with a different name for each iteration of the loop. This scheme is obviously a rotten idea because all the new files end up created, but quite empty. If I take out the $newfilename.txt directive, I get the proper output at stdout so the only problem is with changing the file name in the middle of the game several times. This sounds a bit like a truncation issue. If you do something like command1 bar # some code command2 bar then the second redirect will truncate the file to 0 bytes before redirecting the output from command2 into it. Try using instead of , as it appends to the file. If this doesn't help, please post the script (or a simplified version thereof). We're not clairvoyant, you know... :) HTH, Mario ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
