How to Store Shell Script Output to a Variable

bashcommand-substitutiongithub

I have read many threads on this topic, but none of the solutions have worked for me.

I am trying to do the following:

RELEASE_COMMAND_OUTPUT=$(exec ~/temp/execs/github-release release --user patick --repo $REPO_NAME --tag $RELEASE_VERSION --name $RELEASE_VERSION --description "$DESC")

but the output of ./github-release is not stored in the RELEASE_COMMAND_OUTPUT variable.

I'm aware of the concept of command substitution, but none of the solutions I've tried have worked. What am I doing wrong?

Best Answer

As explained in your question's comments, the variable RELEASE_COMMAND_OUTPUT will only get the STDOUT(standard output) of your command but not the STDERR (standard error), as it seems to be your case.

When in doubt about the output of your command you can use process substitution to mark the STDERR in red as in the following example:

command 2> >(while read line; do echo -e "\e[01;31m$line\e[0m" >&2; done)

Which is redirecting (the 2> part) the STDERR of the command as input to the while block which will print it in red in the terminal.

You can also do the opposite, marking the STDOUT as red with:

command | grep .

Because grep act only in STDOUT

NOTE: in some systems you may need to enable the color in grep using the flag --color=auto. On Macos and Linux usually it's enable by default.

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Try with the --stdout option:

$ SELECTION=$( dialog --stdout \
    --backtitle "Make a choice" \
    --menu "Take a pick" \
    10 40 3 \
    choice1 "First choice" \
    choice2 "Second choice" \
)

Bash – Count number of elements in bash array, where the name of the array is dynamic (i.e. stored in a variable)

you should handle that stuff in the index evals. and you can indirect through your indirection variable's indices if you make it an array.

a=(abc1 def2 ghi3 jkl4 mno5)
r=('a[c=${#a[@]}]' a\[i] a\[@])
for   i in   0 1 2 3 4 5
do    c=
      printf "<%s>\n" "${!r-${!r[i<c?1:2]}}"
      printf "\n\tindex is $i and count is $c\n\n"
done

<abc1>

    index is 0 and count is 5

<def2>

    index is 1 and count is 5

<ghi3>

    index is 2 and count is 5

<jkl4>

    index is 3 and count is 5

<mno5>

    index is 4 and count is 5

<abc1>
<def2>
<ghi3>
<jkl4>
<mno5>

    index is 5 and count is 5

Because bash's indices are 0-based, the total count of array objects will always work out to one more than than the highest set index, and so:

c=
echo "${a[c=${#a[@]}]-this index is unset}" "$c"

this index is unset 5

...the parameter expands out to the default word if any is provided.

If one is not provided:

c=
${!r}
echo "$c"

...there's no harm done.

In the loop I track an $index variable and check if it is at least as large as $count. When it is lesser I expand the $reference var to a[i] because it is a valid index, but when it is equal or greater I expand the $ref to the entire $array.

Here it is in a function:

ref_arr(){
    local    index=-1 count=
    local    ref=(   "$1[ count= \${#$1[@]}  ]"
                     "$1[ index ]"    "$1[ @ ]"
    )  &&    printf  "input array '%s' has '%d' members.\n" \
                     "$1"  "${!ref-${count:?invalid array name: "'$1'"}}"
    while    [ "$((index+=1))" -lt "$count"  ]
    do       printf  "$1[$index]  ==  '%s'\n"  "${!ref[1]}"
    done
}
some_array=(some "dumb
            stuff" 12345\'67890 "" \
          '$(kill my computer)')
ref_arr some_array
ref_arr '$(echo won'\''t work)'

input array 'some_array' has '5' members.
some_array[0]  ==  'some'
some_array[1]  ==  'dumb
                stuff'
some_array[2]  ==  '12345'67890'
some_array[3]  ==  ''
some_array[4]  ==  '$(kill my computer)'
bash: count: invalid array name: '$(echo won't work)'

Best Answer

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Bash – doesn’t `dialog` display the menu (but accepts acceptance) when started through a command substitution expression

Bash – Count number of elements in bash array, where the name of the array is dynamic (i.e. stored in a variable)

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