I have a requirement like i have to remove the strings or numbers between two Parenthesis in a file. I used sed command but it is working on a single line. My opening Parenthesis is in one line and the closing parenthesis is in other line. How can i do it?

I tried this command using sed:

sed -e 's/([^()]*)//g'

but this works only when My opening and closing parenthesis are on the same line.

For Example:-

Input file:

select a
(select e

Output should be:

select a

  • What have you tried - what modifications of the original sed command did you attempt? What were the results? – John Apr 14 '15 at 12:29
  • 1
    For new GNU sed use -z option – Costas Apr 14 '15 at 12:33
  • I tried using sed command sed -e 's/([^()]*)//g' <filename>> this worked for single line ... it didn't worked if parenthesis are on different line – Priyanka Apr 14 '15 at 12:34

Use the following simple perl script to remove every pair of parentheses and their content, even across multiple lines:

undef $/;
$text = <>;
#Flags: g=match repeatedly; s=dot matches newline
$text =~ s/\(.*?\)//gs;
print $text;

If you want to fit it into the commandline, here's the one-liner version:

perl -p0777e 's/\(.*?\)//gs' [filename]

Note that it's shorter and simpler than the perl solutions. -0777 disables the line separator (see the -0 flag under man perlrun), causing the whole file to be processed in one step. Good old perl... It's also (unusually for perl :-)) more readable than messing with sed's pattern space.

  • thanks ... But I need to implement this using Unix only, not perl – Priyanka Apr 15 '15 at 7:51
  • 2
    What do you mean you "have to"? Perl is as much part of unix as sed. If you want something that fits on the commandline, I've added a version. – alexis Apr 15 '15 at 8:34

To remain \new line (if parenthesis in two consequent lines)

sed -e 's/\(^[^)]*) *\)\|([^)]*\() *\|$\)//g' filename

The script consists three patterns:

  • ^[^)]*) * from line begining any symbol(s) exept ) till ) with space(s) after;
  • ([^)]* from ( any symbol(s) exept )
    • till ) with space(s) after; or
    • till $ (end of line)

For multiline cases:

sed ':1;s/([^)]*)//g;/(/{N;b1};' filename
  • But this command is not deleting the content between the opening and closing parenthesis instead it is just removing the lines containing opening and closing parenthesis – Priyanka Apr 14 '15 at 12:51
  • @Priyanka Add for multilines – Costas Apr 14 '15 at 13:16
  • thank u it worked. I am new to unix scripting. need to learn alot – Priyanka Apr 14 '15 at 13:18
  • @Priyanka For future: it is right way to receive correct answer - post example input and desired output – Costas Apr 14 '15 at 13:31

Using Gnu Sed.

-z option (Null separated records), sed slurps all the input as a single record. Please try:

sed -ze 's/([^()]*)//g'

For multi-line matching with sed, it's often easiest to read the whole file, and do your search/replace on the entire contents:

sed -n '            # disable auto-printing
  1h                # first line, move to hold space
  1!H               # not the first line, append to hold space
  ${                # at the end of file
    x               # move hold space to pattern space
    s/([^)]*)//gp   # perform search/replace and print
' file

There are simpler(*) options:

awk -v RS="" '{gsub(/\([^)]+\)/,"")} 1' file
perl -0777 -pe 's/\(.*?\)//sg' file

(*) "simpler" may be in the eye of the beholder ...

  • Just a add On question to this... will it work if i have nested Parenthesis Staements – Priyanka Apr 14 '15 at 13:55
  • 4
    Nope. That kind of structure is beyond what regular expressions can handle. Once you get "nested", your language is no longer regular. – glenn jackman Apr 14 '15 at 15:18

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