redirect error output to function in bash?-CodePudding

How do I redirect the error output from a command to a function?

E.g. I have:

function logit(){
    read output
    echo "error occured -- $output" >> $file
}

mkdir /tmp/pop.txt | logit

But the above doesn't work, the variable "$output" doesn't contain anything.

CodePudding user response：

It's not entirely clear what you mean (in a comment), but perhaps you are looking for something like:

logit(){
    printf "error occured -- ";
    cat
} >> "$file"

exec 3>&1
{
    mkdir /tmp/pop.txt 
    chown ...
    chmod ... 
} 2>&1 1>&3  | logit

This routes the stdout of all the commands in the block to the original stdout of the script while directing the errors streams of all to the logit function. Rather than simply dumping error occurred -- as a header and ignoring newlines in the input, it might be better to implement logit as:

logit(){ sed 's/^/ERROR: /' >> "$file"; }

or maybe even add a timestamp:

logit(){ perl -ne 'printf "%s: ERROR: %s", scalar gmtime, $_'; } >> "$file"