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conditional append one line in file.

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# 1  
Old 04-20-2012
conditional append one line in file.
Hi, Unix gurus,

I have a requirement as following:
checking existing file, if the file only contain one line. then append "No data" else keep existing file as is.
can i achieve this by in command line without write a script.

Smilie

Thanks in advance.
ken002
# 2  
Old 04-20-2012
may be
Code:
NR=`wc -l yourfile`
if [ $NR -eq 1 ]; then
   echo no data >> yourfile
fi

corrected $ before NR.
Moderator's Comments:
Mod Comment code tags for code, please.
Last edited by ajayyadavmca; 04-20-2012 at 04:05 PM..
# 3  
Old 04-20-2012
The above code won't work because of a missing $ in front of NR...

The difference between code in a script and code not in a script is only where you type it.


Code:
[ $(wc -l < filename) -eq 1 ] && echo "No data" >> filename

This User Gave Thanks to Corona688 For This Post:
# 4  
Old 04-20-2012
Quote:
Originally Posted by Corona688
The above code won't work because of a missing $ in front of NR...

The difference between code in a script and code not in a script is only where you type it.


Code:
[ $(wc -l < filename) -eq 1 ] && echo "No data" >> filename

It works!!!
Thanks
This User Gave Thanks to For This Post:
Corona688
ken002
# 5  
Old 04-20-2012
Try an awkie:
Code:
awk 'END{ if(NR==1) print "No data" >> FILENAME }' file

--edit--
This should be more efficient, it only reads 2 lines of the file:
Code:
awk 'getline{exit} {close(FILENAME); print "No data" >> FILENAME }' infile

Last edited by Scrutinizer; 04-20-2012 at 04:46 PM..
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