I have a situation where i want to replace a particular string in many files

Replace a string AAA with another string BBB but there are lot of strings starting with AAA or ending in AAA ,and i want to replace only one on line 34 and keep others intact.

Is it possible to specify by line number,on all files this string is exactly on 34th line.


You can specify line number in sed or NR (number of record) in awk.

awk 'NR==34 { sub("AAA", "BBB") }'

or use FNR (file number record) if you want to specify more than one file on the command line.

awk 'FNR==34 { sub("AAA", "BBB") }'


sed '34s/AAA/BBB/'

to do in-place replacement with sed

sed -i '34s/AAA/BBB/' file_name
  • @VanagaS Thanks, what if I need to replace all the matches I find starting from line 34 and afterwards till EOF? possible entries within lines 1 and 34 shouldn't be touched. thanks Feb 3 '20 at 16:30
  • @ramruma can you give hints? Feb 3 '20 at 16:31
  • @jacquelyn.marquardt you can do something like sed 34,\$s/aaa/bbb/ filename you can find all options using the man pages under the addresses section: man sed
    – Kevin P.
    Feb 15 '20 at 2:52

lets suppose that you want to replace the third line in the file_record:

sed -i "s/`head -3 file_record | tail -1 `/replaced/" file_record
  • use back quote before head and after -1 ... here it is not taking it
    – RAMAN
    Dec 19 '17 at 8:22
  • 1
    This just isn't going to work. It needs some heavy-duty escaping. And what if the third line is duplicated elsewhere?
    – Sparhawk
    Dec 19 '17 at 9:18

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