xref: /freebsd-10-stable/usr.sbin/bsdconfig/share/common.subr

if [ ! "$_COMMON_SUBR" ]; then _COMMON_SUBR=1
#
# Copyright (c) 2012 Ron McDowell
# Copyright (c) 2012-2013 Devin Teske
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
# $FreeBSD: stable/10/usr.sbin/bsdconfig/share/common.subr 258953 2013-12-05 01:06:05Z gjb $
#
############################################################ CONFIGURATION

#
# Default file descriptors to link to stdout/stderr for passthru allowing
# redirection within a sub-shell to bypass directly to the terminal.
#
: ${TERMINAL_STDOUT_PASSTHRU:=3}}
: ${TERMINAL_STDERR_PASSTHRU:=4}}

############################################################ GLOBALS

#
# Program name
#
pgm="${0##*/}"

#
# Program arguments
#
ARGC="$#"
ARGV="$@"

#
# Global exit status variables
#
SUCCESS=0
FAILURE=1

#
# Operating environment details
#
export UNAME_S="$(uname -s)" # Operating System (i.e. FreeBSD)
export UNAME_P="$(uname -p)" # Processor Architecture (i.e. i386)
export UNAME_M="$(uname -m)" # Machine platform (i.e. i386)
export UNAME_R="$(uname -r)" # Release Level (i.e. X.Y-RELEASE)
if [ ! "${PKG_ABI+set}" ]; then
	export PKG_ABI="$(
		ASSUME_ALWAYS_YES=1 pkg -vv |
			awk '$1=="ABI"{print $3;exit}' 2> /dev/null
	)"
fi

#
# Default behavior is to call f_debug_init() automatically when loaded.
#
: ${DEBUG_SELF_INITIALIZE=1}

#
# Default behavior of f_debug_init() is to truncate $debugFile (set to NULL to
# disable truncating the debug file when initializing). To get child processes
# to append to the same log file, export this variarable (with a NULL value)
# and also export debugFile with the desired value.
# 
: ${DEBUG_INITIALIZE_FILE=1}

#
# Define standard optstring arguments that should be supported by all programs
# using this include (unless DEBUG_SELF_INITIALIZE is set to NULL to prevent
# f_debug_init() from autamatically processing "$@" for the below arguments):
#
# 	d	Sets $debug to 1
# 	D:	Sets $debugFile to $OPTARG
#
GETOPTS_STDARGS="dD:"

#
# The getopts builtin will return 1 either when the end of "$@" or the first
# invalid flag is reached. This makes it impossible to determine if you've
# processed all the arguments or simply have hit an invalid flag. In the cases
# where we want to tolerate invalid flags (f_debug_init() for example), the
# following variable can be appended to your optstring argument to getopts,
# preventing it from prematurely returning 1 before the end of the arguments.
#
# NOTE: This assumes that all unknown flags are argument-less.
#
GETOPTS_ALLFLAGS="abcdefghijklmnopqrstuvwxyz"
GETOPTS_ALLFLAGS="${GETOPTS_ALLFLAGS}ABCDEFGHIJKLMNOPQRSTUVWXYZ"
GETOPTS_ALLFLAGS="${GETOPTS_ALLFLAGS}0123456789"

#
# When we get included, f_debug_init() will fire (unless $DEBUG_SELF_INITIALIZE
# is set to disable automatic initialization) and process "$@" for a few global
# options such as `-d' and/or `-D file'. However, if your program takes custom
# flags that take arguments, this automatic processing may fail unexpectedly.
#
# The solution to this problem is to pre-define (before including this file)
# the following variable (which defaults to NULL) to indicate that there are
# extra flags that should be considered when performing automatic processing of
# globally persistent flags.
#
: ${GETOPTS_EXTRA:=}

############################################################ FUNCTIONS

# f_dprintf $format [$arguments ...]
#
# Sensible debug function. Override in ~/.bsdconfigrc if desired.
# See /usr/share/examples/bsdconfig/bsdconfigrc for example.
#
# If $debug is set and non-NULL, prints DEBUG info using printf(1) syntax:
# 	+ To $debugFile, if set and non-NULL
# 	+ To standard output if $debugFile is either NULL or unset
# 	+ To both if $debugFile begins with a single plus-sign (`+')
#
f_dprintf()
{
	[ "$debug" ] || return $SUCCESS
	local fmt="$1"; shift
	case "$debugFile" in ""|+*)
	printf "DEBUG: $fmt${fmt:+\n}" "$@" >&${TERMINAL_STDOUT_PASSTHRU:-1}
	esac
	[ "${debugFile#+}" ] &&
		printf "DEBUG: $fmt${fmt:+\n}" "$@" >> "${debugFile#+}"
	return $SUCCESS
}

# f_debug_init
#
# Initialize debugging. Truncates $debugFile to zero bytes if set.
#
f_debug_init()
{
	#
	# Process stored command-line arguments
	#
	set -- $ARGV
	local OPTIND
	f_dprintf "f_debug_init: ARGV=[%s] GETOPTS_STDARGS=[%s]" \
	          "$ARGV" "$GETOPTS_STDARGS"
	while getopts "$GETOPTS_STDARGS$GETOPTS_EXTRA$GETOPTS_ALLFLAGS" flag \
	> /dev/null; do
		case "$flag" in
		d) debug=1 ;;
		D) debugFile="$OPTARG" ;;
		esac
	done
	shift $(( $OPTIND - 1 ))
	f_dprintf "f_debug_init: debug=[%s] debugFile=[%s]" \
	          "$debug" "$debugFile"

	#
	# Automagically enable debugging if debugFile is set (and non-NULL)
	#
	[ "$debugFile" ] && { [ "${debug+set}" ] || debug=1; }

	#
	# Make debugging persistant if set
	#
	[ "$debug" ] && export debug
	[ "$debugFile" ] && export debugFile

	#
	# Truncate debug file unless requested otherwise. Note that we will
	# trim a leading plus (`+') from the value of debugFile to support
	# persistant meaning that f_dprintf() should print both to standard
	# output and $debugFile (minus the leading plus, of course).
	#
	local _debug_file="${debugFile#+}"
	if [ "$_debug_file" -a "$DEBUG_INITIALIZE_FILE" ]; then
		if ( umask 022 && :> "$_debug_file" ); then
			f_dprintf "Successfully initialized debugFile \`%s'" \
			          "$_debug_file"
			f_isset debug || debug=1 # turn debugging on if not set
		else
			unset debugFile
			f_dprintf "Unable to initialize debugFile \`%s'" \
			          "$_debug_file"
		fi
	fi
}

# f_err $format [$arguments ...]
#
# Print a message to stderr (fd=2).
#
f_err()
{
	printf "$@" >&${TERMINAL_STDERR_PASSTHRU:-2}
}

# f_quietly $command [$arguments ...]
#
# Run a command quietly (quell any output to stdout or stderr)
#
f_quietly()
{
	"$@" > /dev/null 2>&1
}

# f_have $anything ...
#
# A wrapper to the `type' built-in. Returns true if argument is a valid shell
# built-in, keyword, or externally-tracked binary, otherwise false.
#
f_have()
{
	f_quietly type "$@"
}

# f_which $anything [$var_to_set]
#
# A fast built-in replacement for syntaxes such as foo=$( which bar ). In a
# comparison of 10,000 runs of this function versus which, this function
# completed in under 3 seconds, while `which' took almost a full minute.
#
# If $var_to_set is missing or NULL, output is (like which) to standard out.
# Returns success if a match was found, failure otherwise.
#
f_which()
{
	local __name="$1" __var_to_set="$2"
	case "$__name" in */*|'') return $FAILURE; esac
	local __p IFS=":" __found=
	for __p in $PATH; do
		local __exec="$__p/$__name"
		[ -f "$__exec" -a -x "$__exec" ] && __found=1 && break
	done
	if [ "$__found" ]; then
		if [ "$__var_to_set" ]; then
			setvar "$__var_to_set" "$__exec"
		else
			echo "$__exec"
		fi
		return $SUCCESS
	fi
	return $FAILURE
}

# f_getvar $var_to_get [$var_to_set]
#
# Utility function designed to go along with the already-builtin setvar.
# Allows clean variable name indirection without forking or sub-shells.
#
# Returns error status if the requested variable ($var_to_get) is not set.
#
# If $var_to_set is missing or NULL, the value of $var_to_get is printed to
# standard output for capturing in a sub-shell (which is less-recommended
# because of performance degredation; for example, when called in a loop).
#
f_getvar()
{
	local __var_to_get="$1" __var_to_set="$2"
	[ "$__var_to_set" ] || local value
	eval ${__var_to_set:-value}=\"\${$__var_to_get}\"
	eval [ \"\${$__var_to_get+set}\" ]
	local __retval=$?
	eval f_dprintf '"f_getvar: var=[%s] value=[%s] r=%u"' \
		\"\$__var_to_get\" \"\$${__var_to_set:-value}\" \$__retval
	[ "$__var_to_set" ] || { [ "$value" ] && echo "$value"; }
	return $__retval
}

# f_isset $var
#
# Check if variable $var is set. Returns success if variable is set, otherwise
# returns failure.
#
f_isset()
{
	eval [ \"\${${1%%[$IFS]*}+set}\" ]
}

# f_die [$status [$format [$arguments ...]]]
#
# Abruptly terminate due to an error optionally displaying a message in a
# dialog box using printf(1) syntax.
#
f_die()
{
	local status=$FAILURE

	# If there is at least one argument, take it as the status
	if [ $# -gt 0 ]; then
		status=$1
		shift 1 # status
	fi

	# If there are still arguments left, pass them to f_show_msg
	[ $# -gt 0 ] && f_show_msg "$@"

	# Optionally call f_clean_up() function if it exists
	f_have f_clean_up && f_clean_up

	exit $status
}

# f_interrupt
#
# Interrupt handler.
#
f_interrupt()
{
	exec 2>&1 # fix sh(1) bug where stderr gets lost within async-trap
	f_die
}

# f_show_info $format [$arguments ...]
#
# Display a message in a dialog infobox using printf(1) syntax.
#
f_show_info()
{
	local msg
	msg=$( printf "$@" )

	#
	# Use f_dialog_infobox from dialog.subr if possible, otherwise fall
	# back to dialog(1) (without options, making it obvious when using
	# un-aided system dialog).
	#
	if f_have f_dialog_info; then
		f_dialog_info "$msg"
	else
		dialog --infobox "$msg" 0 0
	fi
}

# f_show_msg $format [$arguments ...]
#
# Display a message in a dialog box using printf(1) syntax.
#
f_show_msg()
{
	local msg
	msg=$( printf "$@" )

	#
	# Use f_dialog_msgbox from dialog.subr if possible, otherwise fall
	# back to dialog(1) (without options, making it obvious when using
	# un-aided system dialog).
	#
	if f_have f_dialog_msgbox; then
		f_dialog_msgbox "$msg"
	else
		dialog --msgbox "$msg" 0 0
	fi
}

# f_show_err $format [$arguments ...]
#
# Display a message in a dialog box with ``Error'' i18n title (overridden by
# setting msg_error) using printf(1) syntax. If running non-interactively,
# the process will terminate (using [above] f_die()).
#
f_show_err()
{
	[ "$nonInteractive" ] && f_die

	local msg
	msg=$( printf "$@" )

	: ${msg:=${msg_an_unknown_error_occurred:-An unknown error occurred}}

	if [ "$_DIALOG_SUBR" ]; then
		f_dialog_title "${msg_error:-Error}"
		f_dialog_msgbox "$msg"
		f_dialog_title_restore
	else
		dialog --title "${msg_error:-Error}" --msgbox "$msg" 0 0
	fi
	return $SUCCESS
}

# f_yesno $format [$arguments ...]
#
# Display a message in a dialog yes/no box using printf(1) syntax.
#
f_yesno()
{
	local msg
	msg=$( printf "$@" )

	#
	# Use f_dialog_yesno from dialog.subr if possible, otherwise fall
	# back to dialog(1) (without options, making it obvious when using
	# un-aided system dialog).
	#
	if f_have f_dialog_yesno; then
		f_dialog_yesno "$msg"
	else
		dialog --yesno "$msg" 0 0
	fi
}

# f_noyes $format [$arguments ...]
#
# Display a message in a dialog yes/no box using printf(1) syntax.
# NOTE: THis is just like the f_yesno function except "No" is default.
#
f_noyes()
{
	local msg
	msg=$( printf "$@" )

	#
	# Use f_dialog_noyes from dialog.subr if possible, otherwise fall
	# back to dialog(1) (without options, making it obvious when using
	# un-aided system dialog).
	#
	if f_have f_dialog_noyes; then
		f_dialog_noyes "$msg"
	else
		dialog --defaultno --yesno "$msg" 0 0
	fi
}

# f_show_help $file
#
# Display a language help-file. Automatically takes $LANG and $LC_ALL into
# consideration when displaying $file (suffix ".$LC_ALL" or ".$LANG" will
# automatically be added prior to loading the language help-file).
#
# If a language has been requested by setting either $LANG or $LC_ALL in the
# environment and the language-specific help-file does not exist we will fall
# back to $file without-suffix.
#
# If the language help-file does not exist, an error is displayed instead.
#
f_show_help()
{
	local file="$1"
	local lang="${LANG:-$LC_ALL}"

	[ -f "$file.$lang" ] && file="$file.$lang"

	#
	# Use f_dialog_textbox from dialog.subr if possible, otherwise fall
	# back to dialog(1) (without options, making it obvious when using
	# un-aided system dialog).
	#
	if f_have f_dialog_textbox; then
		f_dialog_textbox "$file"
	else
		dialog --msgbox "$( cat "$file" 2>&1 )" 0 0
	fi
}

# f_include $file
#
# Include a shell subroutine file.
#
# If the subroutine file exists but returns error status during loading, exit
# is called and execution is prematurely terminated with the same error status.
#
f_include()
{
	local file="$1"
	f_dprintf "f_include: file=[%s]" "$file"
	. "$file" || exit $?
}

# f_include_lang $file
#
# Include a language file. Automatically takes $LANG and $LC_ALL into
# consideration when including $file (suffix ".$LC_ALL" or ".$LANG" will
# automatically by added prior to loading the language file).
#
# No error is produced if (a) a language has been requested (by setting either
# $LANG or $LC_ALL in the environment) and (b) the language file does not
# exist -- in which case we will fall back to loading $file without-suffix.
#
# If the language file exists but returns error status during loading, exit
# is called and execution is prematurely terminated with the same error status.
#
f_include_lang()
{
	local file="$1"
	local lang="${LANG:-$LC_ALL}"

	f_dprintf "f_include_lang: file=[%s] lang=[%s]" "$file" "$lang"
	if [ -f "$file.$lang" ]; then
		. "$file.$lang" || exit $?
	else
		. "$file" || exit $?
	fi
}

# f_usage $file [$key1 $value1 ...]
#
# Display USAGE file with optional pre-processor macro definitions. The first
# argument is the template file containing the usage text to be displayed. If
# $LANG or $LC_ALL (in order of preference, respectively) is set, ".encoding"
# will automatically be appended as a suffix to the provided $file pathname.
#
# When processing $file, output begins at the first line containing that is
# (a) not a comment, (b) not empty, and (c) is not pure-whitespace. All lines
# appearing after this first-line are output, including (a) comments (b) empty
# lines, and (c) lines that are purely whitespace-only.
#
# If additional arguments appear after $file, substitutions are made while
# printing the contents of the USAGE file. The pre-processor macro syntax is in
# the style of autoconf(1), for example:
#
# 	f_usage $file "FOO" "BAR"
#
# Will cause instances of "@FOO@" appearing in $file to be replaced with the
# text "BAR" before bering printed to the screen.
#
# This function is a two-parter. Below is the awk(1) portion of the function,
# afterward is the sh(1) function which utilizes the below awk script.
#
f_usage_awk='
BEGIN { found = 0 }
{
	if ( !found && $0 ~ /^[[:space:]]*($|#)/ ) next
	found = 1
	print
}
'
f_usage()
{
	local file="$1"
	local lang="${LANG:-$LC_ALL}"

	f_dprintf "f_usage: file=[%s] lang=[%s]" "$file" "$lang"

	shift 1 # file

	local usage
	if [ -f "$file.$lang" ]; then
		usage=$( awk "$f_usage_awk" "$file.$lang" ) || exit $FAILURE
	else
		usage=$( awk "$f_usage_awk" "$file" ) || exit $FAILURE
	fi

	while [ $# -gt 0 ]; do
		local key="$1"
		export value="$2"
		usage=$( echo "$usage" | awk \
			"{ gsub(/@$key@/, ENVIRON[\"value\"]); print }" )
		shift 2
	done

	f_err "%s\n" "$usage"

	exit $FAILURE
}

# f_index_file $keyword
#
# Process all INDEX files known to bsdconfig and return the path to first file
# containing a menu_selection line with a keyword portion matching $keyword.
#
# If $LANG or $LC_ALL (in order of preference, respectively) is set,
# "INDEX.encoding" files will be searched first.
#
# If no file is found, error status is returned along with the NULL string.
#
# This function is a two-parter. Below is the awk(1) portion of the function,
# afterward is the sh(1) function which utilizes the below awk script.
#
f_index_file_awk='
# Variables that should be defined on the invocation line:
# 	-v keyword="keyword"
BEGIN { found = 0 }
( $0 ~ "^menu_selection=\"" keyword "\\|" ) {
	print FILENAME
	found++
	exit
}
END { exit ! found }
'
f_index_file()
{
	local keyword="$1"
	local lang="${LANG:-$LC_ALL}"

	f_dprintf "f_index_file: keyword=[%s] lang=[%s]" "$keyword" "$lang"

	if [ "$lang" ]; then
		awk -v keyword="$keyword" "$f_index_file_awk" \
			$BSDCFG_LIBE${BSDCFG_LIBE:+/}*/INDEX.$lang &&
			return $SUCCESS
		# No match, fall-thru to non-i18n sources
	fi
	awk -v keyword="$keyword" "$f_index_file_awk" \
		$BSDCFG_LIBE${BSDCFG_LIBE:+/}*/INDEX && return $SUCCESS

	# No match? Fall-thru to `local' libexec sources (add-on modules)

	[ "$BSDCFG_LOCAL_LIBE" ] || return $FAILURE
	if [ "$lang" ]; then
		awk -v keyword="$keyword" "$f_index_file_awk" \
			$BSDCFG_LOCAL_LIBE/*/INDEX.$lang && return $SUCCESS
		# No match, fall-thru to non-i18n sources
	fi
	awk -v keyword="$keyword" "$f_index_file_awk" \
		$BSDCFG_LOCAL_LIBE/*/INDEX
}

# f_index_menusel_keyword $indexfile $pgm
#
# Process $indexfile and return only the keyword portion of the menu_selection
# line with a command portion matching $pgm.
#
# This function is for internationalization (i18n) mapping of the on-disk
# scriptname ($pgm) into the localized language (given language-specific
# $indexfile). If $LANG or $LC_ALL (in orderder of preference, respectively) is
# set, ".encoding" will automatically be appended as a suffix to the provided
# $indexfile pathname.
#
# If, within $indexfile, multiple $menu_selection values map to $pgm, only the
# first one will be returned. If no mapping can be made, the NULL string is
# returned.
#
# If $indexfile does not exist, error status is returned with NULL.
#
# This function is a two-parter. Below is the awk(1) portion of the function,
# afterward is the sh(1) function which utilizes the below awk script.
#
f_index_menusel_keyword_awk='
# Variables that should be defined on the invocation line:
# 	-v pgm="program_name"
#
BEGIN {
	prefix = "menu_selection=\""
	plen = length(prefix)
	found = 0
}
{
	if (!match($0, "^" prefix ".*\\|.*\"")) next

	keyword = command = substr($0, plen + 1, RLENGTH - plen - 1)
	sub(/^.*\|/, "", command)
	sub(/\|.*$/, "", keyword)

	if ( command == pgm )
	{
		print keyword
		found++
		exit
	}
}
END { exit ! found }
'
f_index_menusel_keyword()
{
	local indexfile="$1" pgm="$2"
	local lang="${LANG:-$LC_ALL}"

	f_dprintf "f_index_menusel_keyword: index=[%s] pgm=[%s] lang=[%s]" \
	          "$indexfile" "$pgm" "$lang"

	if [ -f "$indexfile.$lang" ]; then
		awk -v pgm="$pgm" \
			"$f_index_menusel_keyword_awk" \
			"$indexfile.$lang"
	elif [ -f "$indexfile" ]; then
		awk -v pgm="$pgm" \
			"$f_index_menusel_keyword_awk" \
			"$indexfile"
	fi
}

# f_index_menusel_command $indexfile $keyword
#
# Process $indexfile and return only the command portion of the menu_selection
# line with a keyword portion matching $keyword.
#
# This function is for mapping [possibly international] keywords into the
# command to be executed. If $LANG or $LC_ALL (order of preference) is set,
# ".encoding" will automatically be appended as a suffix to the provided
# $indexfile pathname.
#
# If, within $indexfile, multiple $menu_selection values map to $keyword, only
# the first one will be returned. If no mapping can be made, the NULL string is
# returned.
#
# If $indexfile doesn't exist, error status is returned with NULL.
#
# This function is a two-parter. Below is the awk(1) portion of the function,
# afterward is the sh(1) function which utilizes the below awk script.
#
f_index_menusel_command_awk='
# Variables that should be defined on the invocation line:
# 	-v key="keyword"
#
BEGIN {
	prefix = "menu_selection=\""
	plen = length(prefix)
	found = 0
}
{
	if (!match($0, "^" prefix ".*\\|.*\"")) next

	keyword = command = substr($0, plen + 1, RLENGTH - plen - 1)
	sub(/^.*\|/, "", command)
	sub(/\|.*$/, "", keyword)

	if ( keyword == key )
	{
		print command
		found++
		exit
	}
}
END { exit ! found }
'
f_index_menusel_command()
{
	local indexfile="$1" keyword="$2" command
	local lang="${LANG:-$LC_ALL}"

	f_dprintf "f_index_menusel_command: index=[%s] key=[%s] lang=[%s]" \
	          "$indexfile" "$keyword" "$lang"

	if [ -f "$indexfile.$lang" ]; then
		command=$( awk -v key="$keyword" \
				"$f_index_menusel_command_awk" \
				"$indexfile.$lang" ) || return $FAILURE
	elif [ -f "$indexfile" ]; then
		command=$( awk -v key="$keyword" \
				"$f_index_menusel_command_awk" \
				"$indexfile" ) || return $FAILURE
	else
		return $FAILURE
	fi

	#
	# If the command pathname is not fully qualified fix-up/force to be
	# relative to the $indexfile directory.
	#
	case "$command" in
	/*) : already fully qualified ;;
	*)
		local indexdir="${indexfile%/*}"
		[ "$indexdir" != "$indexfile" ] || indexdir="."
		command="$indexdir/$command"
	esac

	echo "$command"
}

# f_running_as_init
#
# Returns true if running as init(1).
#
f_running_as_init()
{
	#
	# When a custom init(8) performs an exec(3) to invoke a shell script,
	# PID 1 becomes sh(1) and $PPID is set to 1 in the executed script.
	#
	[ ${PPID:-0} -eq 1 ] # Return status
}

# f_mounted $local_directory
#
# Return success if a filesystem is mounted on a particular directory.
#
f_mounted()
{
	local dir="$1"
	[ -d "$dir" ] || return $FAILURE
	mount | grep -Eq " on $dir \([^)]+\)$"
}

# f_eval_catch [-d] $funcname $utility $format [$arguments ...]
#
# Silently evaluate a command in a sub-shell and test for error. If debugging
# is enabled a copy of the command and its output is sent to debug (either
# stdout or file depending on environment). If an error occurs, output of the
# command is displayed in a dialog(1) msgbox using the [above] f_show_err()
# function (unless optional `-d' flag is the first argument, then no dialog).
# The $funcname argument is sent to debugging while the $utility argument is
# used in the title of the dialog box. The command that is sent to debugging
# along with $funcname is the product of the printf(1) syntax produced by
# $format with optional $arguments.
#
# Example 1:
#
# 	debug=1
# 	f_eval_catch myfunc cat 'contents=$( cat "%s" )' /some/file
# 	# Error displayed ``cat: /some/file: No such file or directory''
#
# 	Produces the following debug output:
#
# 		DEBUG: myfunc: cat "/some/file"
# 		DEBUG: myfunc: retval=1 <output below>
# 		cat: /some/file: No such file or directory
#
# Example 2:
#
# 	debug=1
# 	f_eval_catch myfunc echo 'echo "%s"' "Hello, World!"
# 	# No error displayed
#
# 	Produces the following debug output:
#
# 		DEBUG: myfunc: echo "Hello, World!"
# 		DEBUG: myfunc: retval=0 <output below>
# 		Hello, World!
#
# Example 3:
#
# 	debug=1
# 	echo 123 | f_eval_catch myfunc rev rev
# 	# No error displayed
#
# 	Produces the following debug output:
#
# 		DEBUG: myfunc: rev
# 		DEBUG: myfunc: retval=0 <output below>
# 		321
#
# Example 4:
#
# 	debug=1
# 	f_eval_catch myfunc true true
# 	# No error displayed
#
# 	Produces the following debug output:
#
# 		DEBUG: myfunc: true
# 		DEBUG: myfunc: retval=0 <no output>
#
f_eval_catch()
{
	local no_dialog=
	[ "$1" = "-d" ] && no_dialog=1 && shift 1
	local funcname="$1" utility="$2"; shift 2
	local cmd output retval
	cmd=$( printf -- "$@" )
	f_dprintf "%s: %s" "$funcname" "$cmd" # Log command *before* eval
	output=$( exec 2>&1; eval "$cmd" )
	retval=$?
	if [ "$output" ]; then
		f_dprintf "%s: retval=%i <output below>\n%s" "$funcname" \
		          $retval "$output"
	else
		f_dprintf "%s: retval=%i <no output>" "$funcname" $retval
	fi
	! [ "$no_dialog" -o "$nonInteractive" -o $retval -eq $SUCCESS ] &&
		msg_error="${msg_error:-Error}${utility:+: $utility}" \
			f_show_err "%s" "$output"
		# NB: f_show_err will handle NULL output appropriately
	return $retval
}

############################################################ MAIN

#
# Trap signals so we can recover gracefully
#
trap 'f_interrupt' SIGINT
trap 'f_die' SIGTERM SIGPIPE SIGXCPU SIGXFSZ \
             SIGFPE SIGTRAP SIGABRT SIGSEGV
trap '' SIGALRM SIGPROF SIGUSR1 SIGUSR2 SIGHUP SIGVTALRM

#
# Clone terminal stdout/stderr so we can redirect to it from within sub-shells
#
eval exec $TERMINAL_STDOUT_PASSTHRU\>\&1
eval exec $TERMINAL_STDERR_PASSTHRU\>\&2

#
# Self-initialize unless requested otherwise
#
f_dprintf "%s: DEBUG_SELF_INITIALIZE=[%s]" \
          dialog.subr "$DEBUG_SELF_INITIALIZE"
case "$DEBUG_SELF_INITIALIZE" in
""|0|[Nn][Oo]|[Oo][Ff][Ff]|[Ff][Aa][Ll][Ss][Ee]) : do nothing ;;
*) f_debug_init
esac

#
# Log our operating environment for debugging purposes
#
f_dprintf "UNAME_S=[%s] UNAME_P=[%s] UNAME_R=[%s]" \
          "$UNAME_S" "$UNAME_P" "$UNAME_R"

f_dprintf "%s: Successfully loaded." common.subr

fi # ! $_COMMON_SUBR