10

I want to run a specific program from a script which normally aks the user for some input (several times).

For example, when I start the program in the shell and my input would be:

t [ENTER]
3 [ENTER]
12 [ENTER]
e [ENTER]

where one has to wait after every line that the program wants the next input.

I guess there is a solution like

echo t | prog
echo 3 | prog
echo 12 | prog
echo e | prog

but after the first line the program runs with no input because of an empty buffer. How can I fix that?

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3 Answers 3

Reset to default
18

Prime use case for a here-document:

prog <<EOF
t
3
12
e
EOF
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Comments

4

Guess it depends on what kind of shell you are using. With bash you can echo multiple lines like,

$ echo "t
> 3
> 12
> e" | prog
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Comments

-2

The read command reads a single line, terminated by a newline. You can include newlines in your echo:

echo "t\n3\n12\ne" | prog

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2 Comments

echo does not handle escape sequences like \n unless -e option is specified on command line. The alternative solution is to use printf.
The bash built-in echo does not handle escape sequences without the -e option, which is a departure from the POSIX standard. Shells like dash, I assume, do not require -e. However, this just supports the suggestion to use printf instead.

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