bash script porting issue related to script program

Question

I am trying to port an existing bash script to Solaris and FreeBSD. It works fine on Fedora and Ubuntu.

This bash script uses the following set of commands to flush the output to the temporary file.

    file=$(mktemp)
    # record test_program output into a temp file
    script -qfc "test_program arg1" "$file" </dev/null &

The script program does not have -qfc options on FreeBSD and Solaris. On Solaris and FreeBSD, script program only has -a option. I have done the following until now:

1) update to latest version of bash. This did not help.

2) Try to find out where exactly is the source code of "script" program is. I could not find it either.

Can somebody help me out here?

git.kernel.org/pub/scm/utils/util-linux/util-linux.git/tree/… — melpomene
– melpomene, Commented Jul 25, 2017 at 8:53
Why is it necessary to capture the output with script? Typically the program is used for interactive sessions. If you just want to capture stdout and stderr use redirection >"$file" 2>&1 instead. — ceving
– ceving, Commented Jul 25, 2017 at 9:22
I think output of the program is not flushed immediately. That is why the script program is being used. — maths-help-seeker
– maths-help-seeker, Commented Jul 25, 2017 at 9:26

Ismael Luceno · Accepted Answer · 2017-07-26 02:30:20Z

2

script is a standalone program, not part of the shell, and as you noticed, only the -a flag is available in all variants. The FreeBSD version supports something similar to -f (-F <file>) and doesn't need -c.

Here's an ugly but more portable solution:

buildsh() {
    cat <<-!
        #!/bin/sh
        SHELL="$SHELL" exec \\
    !
    # Build quoted argument list
    while [ $# != 0 ]; do echo "$1"; shift; done |
    sed  's/'\''/'\'\\\\\'\''/g;s/^/'\''/;s/$/'\''/;!$s/$/ \\/'
}

# Build a shell script with the arguments and run it within `script`
record() {
    local F t="$(mktemp)" f="$1"
    shift
    case "$(uname -s)" in
        Linux) F=-f ;;
        FreeBSD) F=-F ;;
    esac
    buildsh "$@" > "$t" &&
    chmod 500 "$t" &&
    SHELL="$t" script $F "$f" /dev/null
    rm -f "$t"
    sed -i '1d;$d' "$f" # Emulate -q
}

file=$(mktemp)
# record test_program output into a temp file
record "$file" test_program arg1 </dev/null &

edited Jul 26, 2017 at 2:30

answered Jul 26, 2017 at 2:10

Ismael Luceno

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1 Comment

maths-help-seeker Over a year ago

Thanks Ismael. I will try this out.

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