replace

Unlike Bourne Again Shell (bash), POSIX shell does not have a native find/replace function for replacing one occurrence of a pattern in a given string with another. Below is an implementation written in native POSIX shell that is:
Faster than piping to awk, sed, perl, python, ruby, or other langauge
Compatible with bash and all other POSIX-compliant shells
Optimized to use ${parameter/pattern[/string]} when bash is detected
1
 1 #!/bin/sh
2
 2 if [ "$BASH_VERSION" ]; then
3
 3     replace() # $var_to_get $find $replace [$var_to_set]
4
 4     {
5
 5         eval ${4:-$1}=\"\${$1/\$2${3:+/\$3}}\"
6
 6     }
7
 7 else
8
 8     # NB: On FreeBSD, sh(1) runs this faster than bash(1) runs the above
9
 9     replace() # $var_to_get $find $replace [$var_to_set]
10
10     {
11
11         eval local __left= __right=\"\$1\" || return
12
12         case "$__right" in *$2*)
13
13             __left="${__right%%$2*}$3"
14
14             __right="${__right#*$2}"
15
15         esac
16
16         eval ${4:-$1}=\"\$__left\$__right\"
17
17     }
18
18 fi
19
19 eval echo \"before=[\$1]\"
20
20 replace "[email protected]"
21
21 eval echo \" after=[\${4:-$1}]\"
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