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 ${parameter/pattern[/string]} when bash is detected
#!/bin/sh
if [ "$BASH_VERSION" ]; then
   replace() # $var_to_get $find $replace [$var_to_set]
   {
       eval ${4:-$1}=\"\${$1/\$2${3:+/\$3}}\"
   }
else
   # NB: On FreeBSD, sh(1) runs this faster than bash(1) runs the above
   replace() # $var_to_get $find $replace [$var_to_set]
   {
       eval local __left= __right=\"\$1\" || return
       case "$__right" in *$2*)
           __left="${__right%%$2*}$3"
           __right="${__right#*$2}"
       esac
       eval ${4:-$1}=\"\$__left\$__right\"
   }
fi
eval echo \"before=[\$1]\"
replace "[email protected]"
eval echo \" after=[\${4:-$1}]\"

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