add a line between matching pattern - unix

Question

I want to insert "123" below madguy-xyz- line in "module xyz". There are multiple modules having similar lines. But i want to add it in only "module xyz".

module abc 
    njkenjkfvsfd
    madguy-xyz-mafdvnskjfvn
    enfvjkesn
endmodule

module xyz
    njkenjkfvsfd
    madguy-xyz-mafdvnskjfvn
    enfvjkesn
endmodule

This is the code i tried but doesn't work,

sed -i "/module xyz/,/^endmodule/{/madguy-xyz-/a 123}" <file_name>

This is the error I got: sed: -e expression #1, char 0: unmatched `{'

Answer 1

This might work for you (GNU sed):

sed '/module xyz/{:a;n;/madguy-xyz-/!ba;p;s/\S.*/123/}' file

For a line containing module xyz, continue printing lines until one containing madguy-xyz-.

Print this line too and then replace it with 123.

Another alternative solution:

sed '/module/h;G;/madguy-xyz.*\nmodule xyz/{P;s/\S.*/123/};P;d' file

Store any module line in the hold space.

Append the module line to each line.

If the first line contains madguy-xyz- and the second module xyz, print the first then substitute the second for 123.

Print the first line and delete the whole.

Answer 2

With your shown samples, please try following.

awk '1; /^endmodule$/{found=""};/^module xyz$/{found=1} found && /^ +madguy-xyz-/{print "123"} ' Input_file

Once you are happy with results of above command, to save output into Input_file itself try following then:

awk '1;/^endmodule$/{found=""} /^module xyz$/{found=1} found && /^ +madguy-xyz-/{print "123"} ' Input_file > temp && mv temp Input_file

Explanation: Adding detailed explanation for above.

awk '                      ##Starting awk program from here.
1;
/^endmodule$/{found=""}    ##Printing current line here.
/^module xyz$/{            ##Checking condition if line contains module xyz then do following.
  found=1                  ##Setting found to 1 here.
}
found && /^ +madguy-xyz-/{   ##Checking if found is SET and line contains madguy-xyz- then do following.
  print "123"              ##Printing 123 here.
}
' Input_file               ##Mentioning Input_file name here.

NOTE: In case your line exactly having module xyz value then change above /module xyz/ (this condition) to $0=="module xyz" too.