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# Utility functions for use in shell scripts.
## Generate a redirect string for use in reporting errors and the
# like. If no suitable stderr file can be found, returns (prints) an
# empty string.
#
# The redirection operator needs to be included in the output to
# handle the case that we can't figure out where stderr is (so we can
# disable redirection altogether).
get_stderr_redirect()
{
# All of these are symlinks, actually. On my system:
# /dev/stderr -> /dev/fd/2
# /dev/fd -> /proc/self/fd
# /proc/self/fd/2 -> (terminal device, probably the same as the
# output of the `tty' command.)
#
# But I prefer to use the most symbolic one available, because
# /dev/stderr makes more sense than something with numbers in
# it. ;)
for f in '/dev/stderr' '/dev/fd/2' '/proc/self/fd/2'; do
# Use the first one that looks like a character special
# device.
if test -c "$f" ; then
echo "> $f"
return
fi
done
}
## Report a diagnostic message to the user via stderr.
#
# If DETAIL is given, it will be placed below the initial error
# message. DETAIL will be automatically reformatted using fmt from
# coreutils.
#
# Usage: report_oops TYPE MESSAGE [DETAIL]
#
# Output is in the form below.
#
# *** TYPE: MESSAGE
# DETAIL
report_oops()
{
local STR="*** $1: $2"
# If DETAIL is given, append it to the output string after piping
# it through fmt.
if test x"$3" != x ; then
STR="$STR\n`echo '$3' | fmt`"
fi
# Output the message.
#
# To redirect using the computed redirection string (possibly
# empty), we need to use eval.
#
# N.B. the use of proper shell quoting for eval.
eval echo -e "\"$STR\"" `get_stderr_redirect`
}
## Report an error using report_oops.
#
# Usage: report_error MESSAGE [DETAIL]
alias report_error='report_oops ERROR'
## Report a warning using report_oops.
#
# Usage: report_warning MESSAGE [DETAIL]
alias report_warning='report_oops WARNING'
## Report an error and kill the script. Same syntax as report_error.
# Use this to avoid snafus when a critical item fails and you wish to
# abort the script.
die_error()
{
report_error "$@"
exit 1
}
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