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I have a requirement of searching a pattern like x=<followed by any values> from a file and displaying the pattern i.e x=<followed by any values>, only in the screen, not the whole line. How can I do it in Linux?

Alex Bogias
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Sanghamitra Choudhury
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1 Answers1

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I have 3 answers, from simple (but with caveats) to complex (but foolproof):

1) If your pattern never appears more than once per line, you could do this (assuming your shell is 

PATTERN="x="
sed "s/.*\($PATTERN\).*/\1/g" your_file | grep "$PATTERN"

2) If your pattern can appear more than once per line, it's a bit harder. One easy but hacky way to do this is to use a special characters that will not appear on any line that has your pattern, eg, "@":

PATTERN="x="
SPECIAL="@"
grep "$PATTERN" your_file | sed "s/$PATTERN/$SPECIAL/g" \
  | sed "s/[^$SPECIAL]//g" | sed "s/$SPECIAL/$PATTERN/g"

(This won't separate the output pattern per line, eg. you'll see x=x=x= if a source line had 3 times "x=", this is easy to fix by adding a space in the last sed)

3) Something that always works no matter what:

PATTERN="x="
awk "NF>1{for(i=1;i<NF;i++) printf FS; print \"\"}" \
  FS="$PATTERN" your_file
Fabien Viger
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  • Thanks a lot Fabien for the above answer. The above methods will give only "x=" entries whereas I need the output something like , x=3 if I'm assigning x=3 and it is inside a file many times. Please let me know how do I get "x=3" output ,from a file where multiple times "x=3" is repeated inside the file? – Sanghamitra Choudhury Nov 14 '17 at 09:57
  • Some moderators have pointed to an existing answer that will work for your use case too. Applying it to your case will require knowing how the x= is "split" from the following characters in your text files. Assuming that there is always some whitespace (possibly a newline) after the , this would work: `grep -oh "\w*x=\w*" your_file` – Fabien Viger Nov 14 '17 at 23:03
  • Thanks a lot Fabien.It worked. – Sanghamitra Choudhury Nov 17 '17 at 06:07