I am trying to pass output of a command to a variable. Tried many quotes but not successful, please check
I am reading input from a file in $line and processing it, trying to save output in variable a.
set a="$($line|cut -d'-' -f 2|cut -d'.' -f 1|sed 's/[^0-9]*//g’)"
A few things.
The first is that you shouldn't be using set, that's for shell variables rather than environment variables.
Second, unless $line is an actual command, you need to echo it.
Third, your closing quote on the sed command is the wrong type, ’ instead of '.
So, you should be using:
a="$(echo $line|cut -d'-' -f 2|cut -d'.' -f 1|sed 's/[^0-9]*//g')"
You can see this in action in the following transcript:
pax> line="date=2014.09.05-time=12.34.56"
pax> a="$(echo $line|cut -d'-' -f 2|cut -d'.' -f 1|sed 's/[^0-9]*//g')"
pax> echo $a
12
which grabs the second - delimited field (time=12.34.56), then the first . delimited field from that (time=12), then strips off all non-numerics at the start to give just 12.
cut -d'-' -f 2 <<<"$line".
set a=42 sets $1 to the literal string a=42, which is certainly not what OP wanted but doesn't seem to me to correspond to the explanation of why it "doesn't work"... Also, it probably should be echo "$line".Use echo
a="$(echo $line|cut -d'-' -f 2|cut -d'.' -f 1|sed 's/[^0-9]*//g')"
Assuming $filename is the name of the file, you're reading from, you're almost there:
a="$(<$filename cut -d'-' -f 2|cut -d'.' -f 1|sed 's/[^0-9]*//g')"
The problems are:
set, which is not helpful$line) executes it, you want to read from it.//g - you want a simple single quote (') here
Rather than use a long, multi-process pipeline, use the parameter expansion tools provided by the shell itself.
tmp1=${line#*-} # Remove everything up to and include the first -
tmp2=${tmp1%%.*} # Remove everything from the first . onward
a=${tmp2//[!0-9]} # Remove anything that isn't a numerical digit
If you are reading from a file, you can fold the first step into the read command itself
while IFS=- read first second rest; do
tmp=${second%%.*}
a=${tmp//[!0-9]}
done
It may also be simpler to define a regular expression to capture the part of the string you want (a sample line would help in defining such a regex).
[[ $line =~ $regex ]] && a=${BASH_REMATCH[1]} # Assuming the first capture group
