Suppose we have to replace word "four " by "three".
root@root [~]# cat file
one two four
one two four
one two four
one two four
one two four
root@root [~]# replace four three -- file
file converted
root@root [~]# cat file
one two three
one two three
one two three
one two three
one two three
Replaces files in the destination directory with files in the source directory that have the same name. You can also use replace to add unique file names to the destination directory.