Replace whole line when match found with sed

I need to replace the whole line with sed if it matches a pattern. For example if the line is 'one two six three four' and if 'six' is there, then the whole line should be replaced with 'fault'.

You can do it with either of these:

sed 's/.*six.*/fault/' file     # check all lines
sed '/six/s/.*/fault/' file     # matched lines -> then remove

It gets the full line containing six and replaces it with fault.

Example:

$ cat file
six
asdf
one two six
one isix
boo
$ sed 's/.*six.*/fault/'  file
fault
asdf
fault
fault
boo

It is based on this solution to Replace whole line containing a string using Sed

More generally, you can use an expression sed '/match/s/.*/replacement/' file. This will perform the sed 's/match/replacement/' expression in those lines containing match. In your case this would be:

sed '/six/s/.*/fault/' file

---

> What if we have 'one two six eight eleven three four' and we want to > include 'eight' and 'eleven' as our "bad" words?

In this case we can use the -e for multiple conditions:

sed -e 's/.*six.*/fault/' -e 's/.*eight.*/fault/' file

and so on.

Or also:

sed '/eight/s/.*/XXXXX/; /eleven/s/.*/XXXX/' file

Above answers worked fine for me, just mentioning an alternate way

Match single pattern and replace with a new one:

sed -i '/six/c fault' file

Match multiple pattern and replace with a new one(concatenating commands):

sed -i -e '/one/c fault' -e '/six/c fault' file

To replace whole line containing a specified string with the content of that line

Text file:

Row: 0 last_time_contacted=0, display_name=Mozart, _id=100, phonebook_bucket_alt=2
Row: 1 last_time_contacted=0, display_name=Bach, _id=101, phonebook_bucket_alt=2

Single string:

$ sed 's/.* display_name=\([[:alpha:]]\+\).*/\1/'
output:
100
101

Multiple strings delimited by white-space:

$ sed 's/.* display_name=\([[:alpha:]]\+\).* _id=\([[:digit:]]\+\).*/\1 \2/'
output:
Mozart 100
Bach 101

Adjust regex to meet your needs

[:alpha] and [:digit:] are Character Classes and Bracket Expressions

This might work for you (GNU sed):

sed -e '/six/{c\fault' -e ';d}' file

or:

sed '/six/{c\fault'$'\n'';d}' file