I have a following string in a shell script.
var="rule:access=allow,default=default value,OTHER=0,SOMETHING=1"
I need to remove "default=default value" from $var. Thus, the final string will become as follows:
var="rule:access=allow,OTHER=0,SOMETHING=1"
NOTE: The value after default may be anything. It could be "default=something else". It is not fixed. I need to remove that text. How can this be done?
$ echo "$var" | sed 's/default=[^,]*,//'
rule:access=allow,OTHER=0,SOMETHING=1
If we want to update the value of var, we use command substitution:
$ var="$(echo "$var" | sed 's/default=[^,]*,//')"
$ echo "$var"
rule:access=allow,OTHER=0,SOMETHING=1
To remove default=default value,, use pattern substitution:
$ var="${var/default=default value,/}"
$ echo "$var"
rule:access=allow,OTHER=0,SOMETHING=1
This feature is documented in man bash:
${parameter/pattern/string}
Pattern substitution. The pattern is expanded to produce a pattern just as in pathname expansion. Parameter is expanded and the longest match of pattern against its value is replaced with string. If pattern begins with /, all matches of pattern are replaced with string. Normally only the first match is replaced. If pattern begins with #, it must match at the beginning of the expanded value of parameter. If pattern begins with %, it must match at the end of the expanded value of parameter. If string is null, matches of pattern are deleted and the / following pattern may be omitted. If parameter is @ or *, the substitution operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with @ or *, the substitution operation is applied to each member of the array in turn, and the expansion is the resultant list.
$ var="$(echo "$var" | sed 's/default=default value,//')"
$ echo "$var"
rule:access=allow,OTHER=0,SOMETHING=1
Assign this to var again.
echo $var|sed 's/default=default value//'|sed 's/,,/,/'
Last sed to take care of scenarios where default=default value is the first or last keyword in string.
You can use two parameter expansions, one to get the stuff after the comma of default=* and one to get the part before default....
var="rule:access=allow,default=default value,OTHER=0,SOMETHING=1"
endo=${var#*default}
echo ${var/default=*}${endo#*,}
rule:access=allow,OTHER=0,SOMETHING=1
But sed might be easier...!
