Question

I want to run this command in perl

for dir in *; do
 test -d "$dir" && ( find "$dir" -name '*test' | grep -q . || echo "$dir" );
 done

I have tried :

 system ("for dir in *; do
        test -d "\$dir" && ( find "\$dir" -name '*test' | grep -q . || echo "\$dir" );
        done");

but does not work .

Answer 1

Your quoting is off.

"for dir in *; do
    test -d "\$dir" && ( find "\$dir" -name '*test' | grep -q . || echo "\$dir" );
    done"

You have decided to delimit your string with double quotes ", but they are included in your string.

Either escape the other quotes:

"for dir in *; do
    test -d \"\$dir\" && ( find \"\$dir\" -name '*test' | grep -q . || echo \"\$dir\" );
    done"

(error prone, ugly)

… or use another delimiter: Perl offers you a wide range of possibilities. These quoting syntaxes interpolate variables inside: "…" and qq{…} where you can use any character in [^\s\w] as delimiter, and non-interpolating syntaxes are: '…' and q{…} with the same delimiter flexibility as before:

qq{for dir in *; do
    test -d "\$dir" && ( find "\$dir" -name '*test' | grep -q . || echo "\$dir" );
    done}

The q and qq constructs can include the delimiter inside the string, if the occurrence is balanced: q( a ( b ) c ) works.

The third quoting mechanism is a here-doc:

system( <<END_OF_BASH_SCRIPT );
for dir in *; do
    test -d "\$dir" && ( find "\$dir" -name '*test' | grep -q . || echo "\$dir" );
    done
END_OF_BASH_SCRIPT

This is usefull for including longer fragments without worrying about a delimitor. The String is ended by a predefined token that has to appear on a line of its own. If the delimitor declaration is placed in single quotes (<<'END_OF_SCRIPT'), no variables will be interpolated:

system( <<'END_OF_BASH_SCRIPT' );
for dir in *; do
    test -d "$dir" && ( find "$dir" -name '*test' | grep -q . || echo "$dir" );
    done
END_OF_BASH_SCRIPT

Note on the q{} and qq{} syntax: This is a feature never to be used outside of obfuscation, but it is possible to use a character in \w as the delimiter. You have to include a space between the quoting operator q or qq and the delimiter. This works: q xabcx and is equal to 'abc'.