sed stream editor is a very useful utility to manipulate text like replacing patterns, replacing patterns on a certain set of lines etc. We have listed some examples and you might find it useful for text manipulation.

1) sed: How to print nth line of a file?

sed -n 2p /tmp/text  (print line 2 of a file)

2) How to replace text in output (stdout only)?

sed -e ‘s/xxx/yyy/’ <file> (### wont replace file.. will just display)

3) sed: How to replace text in a file?

sed -i ‘s/xxx/yyy/’ <file> (### will do the replacement in file)

4) sed: How to do multiple replacements in one line?

sed -i ‘s/xxx/yyy/;s/abc/yyy/’ <files> (## multiple replacements)

5) sed: How to delete a line(s) using sed?

sed -e ‘4,7d’ <file> ### deletes line 4,7 of file

6) sed: How to replace a given set of lines?

sed -e ‘1,125~s/Jan/AAA/’    ### replace from line 1 to line 125

7) sed: How to add an extra line after each line?

sed G <file>                 # double space a file

8) sed: How to replace a given occurrence in a line?

sed ‘s/foo/bar/4’           # replaces only 4th instance in a line

9) sed: How to replace lines which contain a certain word?

sed ‘/check/s/foo/bar/g’  #### substitute “foo” with “bar” ONLY for lines which contain “check”

10) sed: How to print line with given line numbers?

sed -n ‘8,12p’               # print line 8-12

11) sed: Print first 10 lines of a file.

sed 10q  #print first 10 lines of a file

12) sed: Groupings  – How to swap words in a text?

$ echo “foo bar” |sed -r ‘s/(.*) (.*)/\2 \1/’
bar foo

-r is for extended regex

\1, \2  – matched groups are represented with backslash <number>

13) sed: How to print last 5 lines of a file?

$ cat x.py |sed -n ‘4,$p’

14) sed: Ignore updates in certain lines?

example: updates all lines except 5,6,7,8:

seq 10|sed -r ‘5,8!s/(.*)/\1 x/’
1 x
2 x
3 x
4 x
5
6
7
8
9 x
10 x