Bash – How to resolve this “ambiguous redirect”

bashio-redirectionshell

I have a script with a function in it:

function install_log() {
    echo "$1" >> $INSTALL_LOG_OUTPUT 2>&1
}

This function is working as it should. It is a function to write something into a log file.

I added some other commands to the script, for reading the given parameters of the script:

AUTOMATIC_INSTALL=

for argument in "$@"
do
    install_log "-> parameter $argument"
    if [ "$argument" == "--automatic" ] || ["$argument" == "-automatic" ]; then
        AUTOMATIC_INSTALL=True
    fi
done
install_log "# AUTOMATIC_INSTALL: $AUTOMATIC_INSTALL"

But with the new lines, I get some non needed messages:

$INSTALL_LOG_OUTPUT: ambiguous redirect

I found out, that this comes from the two lines

install_log "-> parameter $argument"
# ...
install_log "# AUTOMATIC_INSTALL: $AUTOMATIC_INSTALL"

Does anyone know, why the messages are occurring.

Best Answer

Put quotes around INSTALL_LOG_OUTPUT in your function, like this:

function install_log() {
    echo "$1" >> "$INSTALL_LOG_OUTPUT" 2>&1
}

After running your script again, you will probably get an error message indicating that INSTALL_LOG_OUTPUT is empty, with a message of this sort: bash: : No such file or directory.

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function startLogging {
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    [ ! -z "$DEBUG" ] && exec 2>&1 || exec 2> >(gawk -v pid=$$ '{ print strftime("%F-%T"),pid,$0; fflush(); }' >>$logfile)
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You need to have $logfile set to something

Bash – Ambiguous output redirect

If you're running (t)csh, you get Ambiguous output redirect. if you try to set up two conflicting redirections:

> echo foo > a > b
Ambiguous output redirect.

In Bash, you could get a similar error if use an array with multiple elements in place of the filename:

$ set aa bb
$ echo foo > "$@"
bash: "$@": ambiguous redirect

As mentioned in answers to stderr redirection not working in csh, the >& operator works in (t)csh to redirect both stdout and stderr. 2>&1 is the standard way to redirect stderr to the same place as stdout, but (t)csh doesn't support that. Instead, it takes the combination > foo 2>&1 as a redirection to foo, a regular argument 2, and a redirection to 1, and the redirections conflict, so you get the error.

>& also works in Bash and zsh, but isn't a standard feature.

Best Answer

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