mjhjmtu

Given

hasArgs=a:b:c:
x=b
if [[ $hasArgs = *$x:* ]] ; then …

I wish I could replace the above double brackets test with a less Bash specific alternative (meaning no subshell/command etc.)

Parameter expansion does not help because it does not expend variables.

if [ "$hasArgs" != "$hasArgs#$x:" ] ; then …

Is there any simple (one line) solution that would fit this use case?

Actually, you can use the standard parameter expansions here (you were just missing the wildcard):

$ args=a:b:c:
$ x=b
$ echo "$args%$x:*"
a:
$ if [ "$args" != "$args#*$x:" ]; then echo 'b: is present'; fi
b: is present

(or equally "$args%$x:*")

The downside is that you need to have the colon after b, so a:b or a plain b wouldn't match, and it would also match a:bb:c. ([[ $var = *$x:* ]] as well as the obvious pattern match with case have the same disadvantage.)

Matching all of b, b:c, a:b, a:b:c, while not matching a:bb:c would be a bit more tricky. All I can think of is something like this:

args=a:b:c
x=b
IFS=: # affects globally
set -f # affects globally...
for x in $args; do
 if [ "$x" = "b" ]; then
 echo "b is present"
 fi
done

Unless you want to write all the cases out:

args=a:b:c
x=b
found=0
case "$args" in
 $x) found=1;;
 $x:*) found=1;;
 *:$x) found=1;;
 *:$x:*) found=1;;
esac
if [ "$found" = 1 ]; then ...; fi

Much easier with regexes (in Bash):

args=b:c
x=b
if [[ $args =~ (^|:)$x(:|$) ]]; then
 echo "b found"
fi

It's not a one-liner, but this is quite readable and can be expanded to check for any number of arguments:

hasArgs="a:b:c"
x=b
case "$hasArgs" in
 *$x*)
 echo "$x is present"
 ;;
esac

The following will work in sh:

if echo "$hasArgs" | grep -q "$x"; then