How to combine timeout and eval commands in bash

问题:

For executing command that is stored in variable the eval command is used:

└──> a="echo -e 'a\nb' | wc -l"
└──> eval $a
2

But how can it be combined with timeout command? I've tried following which gives me wrong output:

└──> timeout 10 $a
'a
b' | wc -l

And the following which gives me errors:

└──> timeout 10 "$a"
timeout: failed to run command `echo -e \'a\\nb\' | wc -l': No such file or directory

└──> timeout 10 $(eval $a)
timeout: failed to run command `2': No such file or directory

└──> timeout 10 $(eval "$a")
timeout: failed to run command `2': No such file or directory

The question can also stand: How can I be sure that following command is executed properly?

timeout 10 "$PROGRAM" "$OPT1" "$OPT2" ...

回答1:

This will work

if timeout "$PROGRAM" "$OPT1" "$OPT2" ... ; then
    echo Program ran successfully
else
    echo Program terminated due to timeout
fi

回答2:

If it's about keeping commands in variables, this will work, although don't know if it's a 'proper bash way' to do it:

command.sh:

#!/bin/bash
echo -e 'a\nb' | wc -l

run.sh:

#!/bin/bash
a="command.sh"
timeout 10 ./$a

回答3:

echo "$(timeout 10 echo -e 'a\nb' | wc -l)"
OR
echo "$(timeout 2 echo "$(eval $a)")"

explanation 1 here : HERE

explanation 2 here : HERE

回答4:

Simple:

eval timeout 10 $a

Output:

2