I have this text file:
some text A=10 some text some more text A more text some other text A=30 other text I'm trying to use sed to capture only the numeric value of A. Using this
cat textfile | sed -r 's/.*A=(\S+).*/\1/' I get:
10 some more text A more text 30 But what i really need is:
10 0 30 If the string A= does not exist output a 0. How can I accomplish this?
I cannot think on a one-liner, so this is my approach:
while read line do grep -Po '(?<=A=)\d+' <<< "$line" || echo "0" done < file I am using the look-behind grep to get any number after A=. In case there is none, the || (else) will print a 0.
I love code-golf!
sed -e 's/^/A=0 /; s/.*\<A=\(\d\+\).*/\1/' This prepends A=0 to the line before substituting.
\< thing making sure you get the last 'A='? What does it actually do?
\< matches the beginning of a wordA= because .* is greedy. That's why we prepend A=0 instead of appending.try this one-liner:
awk -F'A=' 'NF==1{print "0";next}{sub(/ .*/,"",$2);print $2}' file with your data:
kent$ echo "some text A=10 some text some more text A more text some other text A=30 other text"|awk -F'A=' 'NF==1{print "0";next}{sub(/.*/,"",$2);print $2}' 10 0 30 This might work for you (GNU sed):
sed '/.*A=\([0-9][0-9]*\).*/s//\1/;t;s/.*/0/' file Look for the string A= followed by one or more numbers and if it occurs replace the whole line by the back reference. Otherwise replace the whole of the line by 0.
t checks to see if the last substitute command (if any) was a success and if so bails out. As there is no goto place name following the t command it ends the processing of the line. If the substitution was not a success (or no substitute has been done) it replaces the whole line with a 0.I think the best way is to do two different commands - the first replaces lines without 'A=' with the line 'A=0', the second does what you did.
So
cat textfile | sed -r 's/^([^A]|A[^=)*$/A=0/' | sed -r 's/.*A=(\S+).*/\1/' How about:
sed -r -e 's/.*A=(\S+).*/\1/' -e 's/.*A.*/0/' Some grep-sed-cut combination:
grep -o 'A=\?[0-9]*' input | sed 's/A$/A=0/' | cut -d= -f2 Produces:
10 0 30 