You can use variable variables inside the loop so you don’t have to repeat each if block.

To see how they work, try this:
VAR1=abc
abc=123
echo ${!VAR1}

Inside your while read loop you could do something like this:

fred=”"
for VAR in col1 col2 col3 col4; do
if [ -n "${!VAR} ] ; then
fred=$fred”${!VAR}”
fi
done

I have the following code to read in a file an process accordingly :

#/tmp/test.txt looks like this :
# 0-1|0-2|0-3|0-4
# 1-1||1-3|1-4
# |2-2|2-3|2-4
# 3-1|3-2||3-4

FILENAME=$1; #input filename
OIFS=$IFS;
IFS=’|';

while read col1 col2 col3 col4
do
if [ -n "$col1" ]; then
fred=”col1 = ‘$col1′, “;
else
fred=”";
fi
if [ -n "$col2" ]; then
fred=$fred”col2 = ‘$col2′, “;
else
fred=$fred;
fi
if [ -n "$col3" ]; then
fred=$fred”col3 = ‘$col3′, “;
else
fred=$fred;
fi
if [ -n "$col4" ]; then
fred=$fred”col4 = ‘$col4′”;
else
fred=$fred;
fi
echo $fred;
done <$FILENAME

#the output looks like this
col1 = ‘0-1′, col2 = ‘0-2′, col3 = ‘0-3′, col4 = ‘0-4′
col1 = ‘1-1′, col3 = ‘1-3′, col4 = ‘1-4′
col2 = ‘2-2′, col3 = ‘2-3′, col4 = ‘2-4′
col1 = ‘3-1′, col2 = ‘3-2′, col4 = ‘3-4′

I want to know – can I substitute ‘col1 – col4′ for a variable, since there is about 40 fields per line on the “real” file and to do more or less the same validation repetitively seems pointless.

any suggestions would be appreciated.

thanks

I have this BASH,sed, awk, blog to share with all of you.

http://unstableme.blogspot.com/

Thanks for the tips on quoting and nulls!

You can work around the spaces problem very easily in xargs, don’t write it off so soon.

$ cat files.lst
File with spaces.txt
file2.txt

$ cat files.lst |xargs -i rm -v “{}”
removed `File with spaces.txt’
removed `file2.txt’

$cat files.lst |xargs -i echo {}
File with spaces.txt
file2.txt

Using the find command from findutils, you can also specify -print0 to print NUL characters for spaces instead of whitespace. Xargs can them interpret the whitespace via the -0 (that’s a zero) flag. find -print0 and xargs -0 should never fail because UNIX paths won’t contain NULs.

g_m.