ksh - check if String has a pattern

Question

I have a String of command as below:

CMD_LAUNCH="launch.sh \
    -v $ABC_VERSION \
    -p something \
    -X $MAX_HEAP_SPACE_PARAM \
    -Dpersist false \
    -DanotherPasram Abc"

I will launch this command in ksh as below:

$CMD_LAUNCH

How can I make sure the command has -Dpersist false ?

I want to cover the cases where there can be any no of spaces between -Dpersist and false. but my attempt fails to accomplish this.

Try 1)

if [[ "$CMD_LAUNCH" = *"Dpersist\s+false"* ]]
then
        echo "It's there!"
else
        echo "It's not there!"
fi

I want to test if Dpersist false is present in command.

did this using if [[ $ALCYONE_LAUNCHER_CMD = Dpersist+(' ')false ]] is there a better way to represent space than ' ', also how to do I cover tabs as well — Ajeetkumar
– Ajeetkumar, Commented Mar 13, 2018 at 8:02
Thanks for input!. tried that it doesn't work.looks like it's not the regex, it's something like pattern in ksh — Ajeetkumar
– Ajeetkumar, Commented Mar 13, 2018 at 8:31
Why are you using a string instead of a function in the first place? — chepner
– chepner, Commented Mar 14, 2018 at 13:16

rkta · Accepted Answer · 2018-03-14 20:57:05Z

3

Solution 1:

if [[ "$CMD_LAUNCH" == *+(Dpersist+(\s)false)* ]]
then
        echo "It's there!"
else
        echo "It's not there!"
fi

Ksh's pattern matching is different to regex as it will always match the whole string - like regex starting with ^ and ending with $. Therefore you have to enclose the pattern, which itself is enclosed in parentheses, with asterisks. The * matches any sequence of characters. The + in front of each pattern means match 1 or more occurrences of the pattern.

Solution 2:

Another option is to use the =~ operator:

if [[ "$CMD_LAUNCH" =~ Dpersist\s+false ]]                                            
then
    echo "Its there!"
else
     echo "Its not there!"
fi

=~ uses regex syntax.

Resources

For more examples see

Sidenote

Also check out ShellCheck, it helps greatly finding errors in your shell scripts.

edited Mar 14, 2018 at 20:57

answered Mar 13, 2018 at 18:53

rkta

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1 Comment

Ajeetkumar Over a year ago

Solution one fails for multiple cases: 1)ksh k.sh "a.sh -Dpersist true false" 2) ksh k.sh "a.sh -Dpersistfalse" 3) ksh k.sh "a.sh"

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