Variables as commands in Bash scripts
I am writing a very simple Bash script that tars a given directory, encrypts the output of that, and then splits the resultant file into multiple smaller files since the backup media doesn’t support huge files.
I don't have a lot of experience with Bash scripting. I believe I’m having issues with quoting my variables properly to allow spaces in the parameters. The script follows:
#! /bin/bash # This script tars the given directory, encrypts it, and transfers # it to the given directory (likely a USB key). if [ $# -ne 2 ] then echo "Usage: `basename $0` DIRECTORY BACKUP_DIRECTORY" exit 1 fi DIRECTORY=$1 BACKUP_DIRECTORY=$2 BACKUP_FILE="$BACKUP_DIRECTORY/`date +%Y-%m-%dT%H-%M-%S.backup`" TAR_CMD="tar cv $DIRECTORY" SPLIT_CMD="split -b 1024m - "$BACKUP_FILE"" ENCRYPT_CMD='openssl des3 -salt' echo "$TAR_CMD | $ENCRYPT_CMD | $SPLIT_CMD" $TAR_CMD | $ENCRYPT_CMD | $SPLIT_CMD say "Done backing up"
Running this command fails with:
split: "foo/2009-04-27T14-32-04.backup"aa: No such file or directory
I can fix it by removing the quotes around
$BACKUP_FILE where I set
$SPLIT_CMD. But, if I have a space in the name of my backup directory, it doesn't work. Also, if I copy and paste the output from the "echo" command directly into the terminal, it works fine. Clearly there's something I don't understand about how Bash is escaping things.