<<Anchor(faq40)>>
== How do I use dialog to get input from the user? ==
Here is an example:

{{{#!highlight bash
# POSIX
foo=$(dialog --inputbox "text goes here" 8 40 2>&1 >/dev/tty)
printf "The user typed '%s'\n" "$foo"
}}}

The redirection here is a bit tricky.

 1. The {{{foo=$(command)}}} is set up first, so the standard output of the command is being captured by bash.

 1. Inside the command, the {{{2>&1}}} causes standard error to be sent to where standard out is going -- in other words, stderr will now be captured.

 1. {{{>/dev/tty}}} sends standard output to the terminal, so the dialog box will be seen by the user.  Standard error will still be captured, however.

Another common {{{dialog(1)}}}-related question is how to dynamically generate a dialog command that has items which must be quoted (either because they're empty strings, or because they contain internal white space).  One ''can'' use {{{eval}}} for that purpose, but the cleanest way to achieve this goal is to use an [[BashFAQ/005|array]].

{{{#!highlight bash
# Bash
unset -v m; i=0
words=(apple banana cherry "dog droppings")
for w in "${words[@]}"; do
    m[i++]=$w; m[i++]=""
done
dialog --menu "Which one?" 12 70 9 "${m[@]}"
}}}

In this example, the while loop that populates the '''m''' array could have been reading from a pipeline, a file, etc.

Recall that the construction {{{"${m[@]}"}}} expands to the entire contents of an array, but with each element implicitly quoted.  It's analogous to the {{{"$@"}}} construct for handling positional parameters.  For more details, see [[BashFAQ/050|FAQ #50]].

Newer [[BashFAQ/061|versions of bash]] have a slightly prettier syntax for appending elements to an array:
{{{#!highlight bash
# Bash 3.1 and up
...
for w in "${words[@]}"; do
    m+=("$w" "")
done
...
}}}

Here's another example, using filenames:

{{{#!highlight bash
# Bash
files=(*.mp3)       # These may contain spaces, apostrophes, etc.
cmd=(dialog --menu "Select one:" 22 76 16)
i=0 n=${#cmd[*]}
for i in "${!files[@]}"; do
    cmd[n++]=$i; cmd[n++]=${files[i]}
done
choice=$("${cmd[@]}" 2>&1 >/dev/tty)
printf "Here's the file you chose:\n"
ls -ld -- "${files[choice]}"
}}}

A separate but useful function of dialog is to track progress of a process that produces output. Below is an example that uses dialog to track processes writing to a log file. In the dialog window, there is a tailbox where output is stored, and a msgbox with a clickable Quit. Clicking quit will cause trap to execute, removing the tempfile, and destroying the tail process.

{{{#!highlight bash
# POSIX
# you cannot tail a nonexistent file, so always ensure it pre-exists!
> dialog-tail.log
{
    for i in 1 2 3; do
        printf '%d\n' "$i"
        sleep 1
    done

    printf 'Done\n'
} > dialog-tail.log &

dialog --title "TAIL BOXES" \
       --begin 10 10 --tailboxbg dialog-tail.log 8 58 \
       --and-widget \
       --begin 3 10 --msgbox "Press OK " 5 30

wait
}}}

For an example of creating a progress bar using {{{dialog --gauge}}}, see [[BashFAQ/044|FAQ #44]].

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CategoryShell