Replacing string based on line number

Question

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.

score 149 · Accepted Answer · edited Aug 08 '16 at 16:48

149

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") }'

or

sed '34s/AAA/BBB/'

to do in-place replacement with sed

sed -i '34s/AAA/BBB/' file_name

edited Aug 08 '16 at 16:48

VanagaS

774

answered Apr 02 '13 at 05:00

@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 – Jacquelyn.Marquardt Feb 03 '20 at 16:30
@ramruma can you give hints? – Jacquelyn.Marquardt Feb 03 '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 02:52

score -3 · Answer 2 · edited Dec 19 '17 at 08:23

-3

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

edited Dec 19 '17 at 08:23

muru

72,889

answered Dec 19 '17 at 08:20

RAMAN

1

use back quote before head and after -1 ... here it is not taking it – RAMAN Dec 19 '17 at 08:22
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 09:18

Replacing string based on line number

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