replaceall

Unlike Bourne Again Shell (bash), POSIX shell does not have a native find/replace function for replacing all occurrences 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 #!/bin/sh
 2 if [ "$BASH_VERSION" ]; then
 3     replaceall() # $var_to_get $find $replace [$var_to_set]
 4     {
 5         eval ${4:-$1}=\"\${$1//\$2${3:+/\$3}}\"
 6     }
 7 else
 8     # NB: On FreeBSD, sh(1) runs this faster than bash(1) runs the above
 9     replaceall() # $var_to_get $find $replace [$var_to_set]
10     {
11         eval local __left= __right=\"\$$1\" || return
12         while :; do
13             case "$__right" in *$2*)
14                 __left="$__left${__right%%$2*}$3"
15                 __right="${__right#*$2}"
16                 continue
17             esac
18             break
19         done
20         __left="$__left${__right#*$2}"
21         eval ${4:-$1}=\"\$__left\"
22     }
23 fi
24 eval echo \"before=[\$$1]\"
25 replaceall "$@"
26 eval echo \" after=[\$${4:-$1}]\"