Shell Programming and Scripting

If there is any possibility that there might not be any matching files, adding the test for no matching files is a great idea. But:

Code:

${i/1/2}

expands to the contents of $i with the first occurrence of 1 changed to 2; not all occurrences.

The syntax to replace all occurrences of a pattern with a replacement string is:

Code:

${i//pattern/replacement}

The syntax to replace an occurrence of a pattern only if it is at the start of the expansion is:

Code:

${i/#pattern/replacement}

The syntax to replace an occurrence of a pattern only if it is at the end of the expansion is:

Code:

${i/%pattern/replacement}

For example:

Code:

$ x=1x1x1
$ echo ${x/1/2}
2x1x1
$ echo ${x//1/2}
2x2x2
$ echo ${x/#1/2}
2x1x1
$ echo ${x/%1/2}
1x1x2
$

None of these parameter expansions are in the standards. But they all work in 1993 or later versions of ksh and in recent versions of bash.