bash - logging

[Notgnoshi]

• echo with output redirection (see Bash - redirections and pipes #99)
• log levels with argument parsing (see Bash argument parsing #50)
• dump xtrace output to a file (file, or /dev/kmsg for debugging boot issues) (see http://mywiki.wooledge.org/BashGuide/Practices#Debugging)
• redirect xtrace output to a command like logger(1)

---

#!/bin/bash
function trace()
{
    logger -s "TRACE ${BASH_SOURCE[1]}:${BASH_LINENO[0]}:${FUNCNAME[1]}: $BASH_COMMAND"
}
set -o functrace
shopt -s extdebug
trap trace DEBUG

---

# dump set -x data to a file
# turns on with a filename as $1
# turns off with no params
# note that FD 4 should not be used elsewhere in the script
setx_output()
{
    if [[ $1 ]]; then
        exec 4>>"$1"
        BASH_XTRACEFD=4
        set -x
    else
        set +x
        exec 4>&-
    fi
}