pass a password to an application

Shell Programming and Scripting
1

Hi folks

I am new to shellscripting and I try to automate & guify some jobs.
Suppose I have a variable the stores a passwd and an application like "gpg" or "zip" to run from withn the script.

how do I pass that passwd (the content of the variable) to the application being called?

eg.

#/bin/bash
passwd=$1
gpg -d ~/thegpgfile.gpg

running this my terminal sits there waiting for me to enter a passwd. How do I automaticaly use the $passwd so the script continues execution without me interacting?

thank you in advance

p.s. excuse the english. its not me native language

2

For better control, you may want to try out "Expect" scripting - Expect - Expect - Home Page

Whereas a kludge using just shell scripts is as follows:

$ 
$ file testfile.*
testfile.gpg: GPG encrypted data
$ 
$ cat decrypt.sh
#!/bin/bash
gpg --output testfile.txt --decrypt testfile.gpg

$ 
$ cat passphrase.txt
disneyland
$ 
$ . decrypt.sh <passphrase.txt

You need a passphrase to unlock the secret key for
user: "Alice"
2048-bit ELG-E key, ID 46972146, created 2009-07-18 (main key ID 53FD32A9)

gpg: encrypted with 2048-bit ELG-E key, ID 46972146, created 2009-07-18
      "Alice"
$ 
$ file testfile.*
testfile.gpg: GPG encrypted data
testfile.txt: ASCII text
$ 
$ cat testfile.txt
this is a test file
that I'd like to encrypt/decrypt
using gpg
$ 
$

tyler_durden

3

As for GPG, there's been a lengthy thread here, with a lot of explanation.

4

I real dont want to use expect because of portability issues.
No offense...but I realy dont undersatnd your example...I see what you are doing...but what are you trying to say?

for now I am using this line:

`echo 'thepassword | gpg --passphrase-fd 0 -d thefile.gpg`

but that only gets me around the gpg issue, but not the core of the question -> how to pass strings to a running peece of code?!

further question:

how do I put a file (its content whether text or binary) into a shell variable?
This right here is not working:

file=`echo 'thepassword | gpg --passphrase-fd 0 -d thefile.gpg`
file $file
FILETYPE=`file $file | cut -d " " -f 2`
echo "$FILETYPE"

souldn't file tell me something like this:

[UTF-8 Unicode text
5

There isn't one well defined way of passing a password to a program. Some you can echo to, others won't allow that (ssh for example). gpg only allows it with the --passphrase-fd option.

As for your example: the file utility works on files. There's no option to read from a pipe. Better save the content to a temporary file, run file on it, and then read the content back into a variable with cat (or any other mechanism your shell might provide)