Can I join two commands defined as String and run as one. E.g.
var="ls -alt"
var2="| grep usersfile"
var3="| grep usersfolder"
Following example for joining commands does not work.
a. '{$var & $var2;}'
b. '{$var & $var3;}'
What I what is:
a. run "$var $var2" and get "ls -alt | grep usersfile"
or
b. run "$var $var3" and get "ls -alt | grep usersfolder"
Yes, you can do this by using eval.
$ var="ls -alt"
$ var2="| grep usersfile"
$ var3="| grep usersfolder"
$ eval "$var$var2"
< Output of ls -alt | grep userfile >
$ eval "$var$var3"
< Output of ls -alt | grep usersfolder >
You probably shouldn't do it this way. Depending on what you are actually trying to accomplish there are likely other options:
If you are just trying to have a dynamic option to select your search string you could do something like this instead:
#!/bin/bash
pattern=$1
ls -alt | grep "${pattern:-.}"
This will search for whatever your first positional parameter is, or anything if none is provided.
Or if you're trying to act on some condition:
#!/bin/bash
cmd=(ls -alt)
p1=usersfile
p2=usersfolder
if [[ condition1 ]]; then
p=$p1
elif [[ condition2 ]]; then
p=$p2
fi
"${cmd[@]}" | grep "$p"
Or in a function:
#!/bin/bash
ls_func () {
local p=$1
ls -alt | grep "${p:-.}"
}
while getopts p:c: opt; do
case $opt in
c) command=$OPTARG;;
p) pattern=$OPTARG;;
esac
done
if [[ $command == 'ls' ]]; then
ls_func "$pattern"
fi
a. '{ etc. }'andb. '{ etc. }'. Do you want to assign the "joint command" to a variableaandbrespectively which you then want to "execute"?ls -ltoutput for something containing the stringuserfolderand/or the stringuserfile. Could you rephrase your question to show what the underlying issue is. Grepping the output oflsis very rarely the correct approach. For example, why would you need to store thelscommand in a variable? Why not create a shell function instead?