= Expect =

'''`expect(1)`''' is a tool and scripting language for automating interactive command line tools.

<<TableOfContents>>

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== Example ==

Consider the `age(1)` encryption tool, which supports passphrase (symmetric key) encryption but does not support passing the passphrase in plain text.

{{{
$ tar -c example.txt | age --encrypt --passphrase > example.tar.age
Enter passphrase (leave empty to autogenerate a secure one):
Confirm passphrase:
}}}

To automate this exchange, try:

{{{
expect <<EOF
spawn sh -c "age --encrypt --passphrase example.tar > example.tar.age"
expect "*:"
send "test123\r"
expect "*:"
send "test123\r"
expect eof
EOF
}}}

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== Installation ==

Most [[Linux]] and [[BSD]] distributions offer an `expect` package.

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== Syntax ==

'''`spawn`''' executes a singular command. To spawn a pipeline of commands, instead spawn a shell process with the pipeline passed as a command string.

'''`expect`''' reads output from the spawned process and conditionally dispatches to further logic.

'''`send`''' submits some message to the spawned process. Typically it is necessary to specify the newline (using `\r`) at the end of the message.



=== Passing exit codes ===

To pass an exit code from a spawned process, try:

{{{
foreach {pid spawnid os_error_flag value} [wait] break
exit $value
}}}



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CategoryRicottone