sysrc(8) -- a sysctl(8)-like utility for managing rc.conf(5)
Devin Teske
devin.teske at fisglobal.com
Tue Oct 12 23:27:51 UTC 2010
Hey all,
Long-time user, first-time poster (to this list at least).
Over on the -hackers@ mailing-list, I posted the first version of a
script I've written named sysrc(8), designed to ease management of the
rc.conf(5) files. There were a lot of great discussions about this over
on -hackers@: http://lists.freebsd.org/pipermail/freebsd-hackers/2010-
October/thread.html
I'm now happy to post the second version of this script which attempts
to address all of the concerns that -hackers@ brought-up.
Behold... sysrc(8) v2.0
NOTE: just scroll down a little to the INFORMATION section for an easy-
to-read usage statement.
#!/bin/sh
# -*- tab-width: 4 -*- ;; Emacs
# vi: set tabstop=4 :: Vi/ViM
#
# Revision: 2.0
# Last Modified: October 12th, 2010
############################################################ COPYRIGHT
#
# (c)2010. 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.
#
# AUTHOR DATE DESCRIPTION
# dteske 2010.10.12 Updates per freebsd-hackers thread.
# dteske 2010.09.29 Initial version.
#
############################################################ INFORMATION
#
# Command Usage:
#
# sysrc [OPTIONS] name[=value] ...
#
# OPTIONS:
# -h Print this message to stderr and exit.
# -f file Operate on the specified file(s) instead of rc_conf_files.
# -a Dump a list of non-default configuration variables.
# -A Dump a list of all configuration variables (incl. defaults).
# -d Print a description of the given variable.
# -e Print query results as `var=value' (useful for producing
# output to be fed back in). Ignored if -n is specified.
# -v Verbose. Print the pathname of the specific rc.conf(5)
# file where the directive was found.
# -i Ignore unknown variables.
# -n Show only variable values, not their names.
# -N Show only variable names, not their values.
#
# ENVIRONMENT:
# RC_DEFAULTS Location of `/etc/defaults/rc.conf' file.
# SYSRC_VERBOSE Default verbosity. Set to non-NULL to enable.
#
############################################################ CONFIGURATION
#
# Default verbosity.
#
: ${SYSRC_VERBOSE:=}
#
# Default location of the rc.conf(5) defaults configuration file.
#
: ${RC_DEFAULTS:="/etc/defaults/rc.conf"}
############################################################ GLOBALS
#
# Global exit status variables
#
SUCCESS=0
FAILURE=1
#
# Program name
#
progname="${0##*/}"
#
# Options
#
DESCRIBE=
RC_CONFS=
IGNORE_UNKNOWNS=
SHOW_ALL=
SHOW_EQUALS=
SHOW_NAME=1
SHOW_VALUE=1
############################################################ FUNCTION
# fprintf $fd $fmt [ $opts ... ]
#
# Like printf, except allows you to print to a specific file-descriptor. Useful
# for printing to stderr (fd=2) or some other known file-descriptor.
#
fprintf()
{
local fd=$1
[ $# -gt 1 ] || return $FAILURE
shift 1
printf "$@" >&$fd
}
# eprintf $fmt [ $opts ... ]
#
# Print a message to stderr (fd=2).
#
eprintf()
{
fprintf 2 "$@"
}
# die [ $fmt [ $opts ... ]]
#
# Optionally print a message to stderr before exiting with failure status.
#
die()
{
local fmt="$1"
[ $# -gt 0 ] && shift 1
[ "$fmt" ] && eprintf "$fmt\n" "$@"
exit $FAILURE
}
# usage
#
# Prints a short syntax statement and exits.
#
usage()
{
local optfmt="\t%-11s%s\n"
local envfmt="\t%-17s%s\n"
eprintf "Usage: %s [OPTIONS] name[=value] ...\n" "$progname"
eprintf "OPTIONS:\n"
eprintf "$optfmt" "-h" \
"Print this message to stderr and exit."
eprintf "$optfmt" "-f file" \
"Operate on the specified file(s) instead of rc_conf_files."
eprintf "$optfmt" "-a" \
"Dump a list of non-default configuration variables."
eprintf "$optfmt" "-A" \
"Dump a list of all configuration variables (incl. defaults)."
eprintf "$optfmt" "-d" \
"Print a description of the given variable."
eprintf "$optfmt" "-e" \
"Print query results as \`var=value' (useful for producing"
eprintf "$optfmt" "" \
"output to be fed back in). Ignored if -n is specified."
eprintf "$optfmt" "-v" \
"Verbose. Print the pathname of the specific rc.conf(5)"
eprintf "$optfmt" "" \
"file where the directive was found."
eprintf "$optfmt" "-i" \
"Ignore unknown variables."
eprintf "$optfmt" "-n" \
"Show only variable values, not their names."
eprintf "$optfmt" "-N" \
"Show only variable names, not their values."
eprintf "\n"
eprintf "ENVIRONMENT:\n"
eprintf "$envfmt" "RC_DEFAULTS" \
"Location of \`/etc/defaults/rc.conf' file."
eprintf "$envfmt" "SYSRC_VERBOSE" \
"Default verbosity. Set to non-NULL to enable."
die
}
# clean_env [ --except $varname ... ]
#
# Unset all environment variables in the current scope. An optional list of
# arguments can be passed, indicating which variables to avoid unsetting; the
# `--except' is required to enabled the exclusion-list as the remainder of
# positional arguments.
#
# Be careful not to call this in a shell that you still except to perform
# $PATH expansion in, because this will blow $PATH away. This is best used
# within a sub-shell block "(...)" or "$(...)" or "`...`".
#
clean_env()
{
local var arg except=
#
# Should we process an exclusion-list?
#
if [ "$1" = "--except" ]; then
except=1
shift 1
fi
#
# Loop over a list of variable names from set(1) built-in.
#
for var in $( set | awk -F= \
'/^[[:alpha:]_][[:alnum:]_]*=/ {print $1}' \
| grep -v '^except$'
); do
#
# In POSIX bourne-shell, attempting to unset(1) OPTIND results
# in "unset: Illegal number:" and causes abrupt termination.
#
[ "$var" = OPTIND ] && continue
#
# Process the exclusion-list?
#
if [ "$except" ]; then
for arg in "$@" ""; do
[ "$var" = "$arg" ] && break
done
[ "$arg" ] && continue
fi
unset "$var"
done
}
# sysrc_get $varname
#
# Get a system configuration setting from the collection of system-
# configuration files (in order: /etc/defaults/rc.conf /etc/rc.conf
# and /etc/rc.conf).
#
# NOTE: Additional shell parameter-expansion formats are supported. For
# example, passing an argument of "hostname%%.*" (properly quoted) will
# return the hostname up to (but not including) the first `.' (see sh(1),
# "Parameter Expansion" for more information on additional formats).
#
sysrc_get()
{
# Sanity check
[ -f "$RC_DEFAULTS" -a -r "$RC_DEFAULTS" ] || return $FAILURE
# Taint-check variable name
case "$1" in
[0-9]*)
# Don't expand possible positional parameters
return $FAILURE;;
*)
[ "$1" ] || return $FAILURE
esac
( # Execute within sub-shell to protect parent environment
#
# Clear the environment of all variables, preventing the
# expansion of normals such as `PS1', `TERM', etc.
#
clean_env --except RC_CONFS RC_DEFAULTS
. "$RC_DEFAULTS"
#
# If `-f file' was passed, set $rc_conf_files to an explicit
# value, modifying the default behavior of source_rc_confs().
#
[ "$RC_CONFS" ] && rc_conf_files="$RC_CONFS"
unset RC_CONFS
# no longer needed
source_rc_confs
#
# This must be the last functional line for both the sub-shell,
# and the function to preserve the return status from formats
# such as "${varname?}" and "${varname:?}" (see "Parameter
# Expansion" in sh(1) for more information).
#
eval echo '"${'"$1"'}"' 2> /dev/null
)
}
# sysrc_find $varname
#
# Find which file holds the effective last-assignment to a given variable
# within the rc.conf(5) file(s).
#
# If the variable is found in any of the rc.conf(5) files, the function prints
# the filename it was found in and then returns success. Otherwise output is
# NULL and the function returns with error status.
#
sysrc_find()
{
local varname="$1"
local rc_conf_files="$( sysrc_get rc_conf_files )"
local conf_files=
local file
# Check parameters
[ "$varname" ] || return $FAILURE
#
# If `-f file' was passed, set $rc_conf_files to an explicit
# value, modifying the default behavior of source_rc_confs().
#
[ "$RC_CONFS" ] && rc_conf_files="$RC_CONFS"
#
# Reverse the order of files in rc_conf_files (the boot process sources
# these in order, so we will search them in reverse-order to find the
# last-assignment -- the one that ultimately effects the environment).
#
for file in $rc_conf_files; do
conf_files="$file${conf_files:+ }$conf_files"
done
#
# Append the defaults file (since directives in the defaults file
# indeed affect the boot process, we'll want to know when a directive
# is found there).
#
conf_files="$conf_files${conf_files:+ }$RC_DEFAULTS"
#
# Find which file matches assignment to the given variable name.
#
for file in $conf_files; do
if grep -q "^[[:space:]]*$varname=" $file; then
echo $file
return $SUCCESS
fi
done
return $FAILURE # Not found
}
# ... | lrev
# lrev $file ...
#
# Reverse lines of input. Unlike rev(1) which reverses the ordering of
# characters on a single line, this function instead reverses the line
# sequencing.
#
# For example, the following input:
#
# Line 1
# Line 2
# Line 3
#
# Becomes reversed in the following manner:
#
# Line 3
# Line 2
# Line 1
#
lrev()
{
local stdin_rev=
if [ $# -gt 0 ]; then
#
# Reverse lines from files passed as positional arguments.
#
while [ $# -gt 0 ]; do
local file="$1"
[ -f "$file" ] && lrev < "$file"
shift 1
done
else
#
# Reverse lines from standard input
#
while read -r LINE; do
stdin_rev="$LINE
$stdin_rev"
done
fi
echo -n "$stdin_rev"
}
# sysrc_set $varname $new_value
#
# Change a setting in the system configuration files (edits the files in-place
# to change the value in the last assignment to the variable). If the variable
# does not appear in the source file, it is appended to the end of the primary
# system configuration file `/etc/rc.conf'.
#
sysrc_set()
{
local varname="$1" new_value="$2"
# Check arguments
[ "$varname" ] || return $FAILURE
#
# Find which rc.conf(5) file contains the last-assignment
#
local not_found=
local file="$( sysrc_find "$varname" )"
if [ "$file" = "$RC_DEFAULTS" -o ! "$file" ]; then
#
# We either got a null response (not found) or the variable
# was only found in the rc.conf(5) defaults. In either case,
# let's instead modify the first file from $rc_conf_files.
#
not_found=1
#
# If `-f file' was passed, use $RC_CONFS
# rather than $rc_conf_files.
#
if [ "$RC_CONFS" ]; then
file="${RC_CONFS%%[$IFS]*}"
else
file="$( sysrc_get "rc_conf_files%%[$IFS]*" )"
fi
fi
#
# Perform sanity checks.
#
if [ ! -w $file ]; then
eprintf "\n%s: cannot create %s: Permission denied\n" \
"$progname" "$file"
return $FAILURE
fi
#
# If not found, append new value to last file and return.
#
if [ "$not_found" ]; then
echo "$varname=\"$new_value\"" >> "$file"
return $SUCCESS
fi
#
# Operate on the matching file, replacing only the last occurrence.
#
local new_contents="`lrev $file 2> /dev/null | \
( found=
while read -r LINE; do
if [ ! "$found" ]; then
match="$( echo "$LINE" | grep "$regex" )"
if [ "$match" ]; then
LINE="$varname"'="'"$new_value"'"'
found=1
fi
fi
echo "$LINE"
done
) | lrev`"
[ "$new_contents" ] || return $FAILURE
#
# Create a new temporary file to write to.
#
local tmpfile="$( mktemp -t "$progname" )"
[ "$tmpfile" ] || return $FAILURE
#
# Fixup permissions (else we're in for a surprise, as mktemp(1) creates
# the temporary file with 0600 permissions, and if we simply mv(1) the
# temporary file over the destination, the destination will inherit the
# permissions from the temporary file).
#
chmod $( stat -f '%#Lp' "$file" ) "$tmpfile" 2> /dev/null
#
# Fixup ownerhsip. The destination file _is_ writable (we tested
# earlier above). However, this will fail if we don't have sufficient
# permissions (so we throw stderr into the bit-bucket).
#
chown $( stat -f '%u:%g' "$file" ) "$tmpfile" 2> /dev/null
#
# Write the temporary file contents and move it into place.
#
echo "$new_contents" > "$tmpfile" || return $FAILURE
mv "$tmpfile" "$file"
}
# sysrc_desc $varname
#
# Attempts to return the comments associated with varname from the rc.conf(5)
# defaults file `/etc/defaults/rc.conf' (or whatever RC_DEFAULTS points to).
#
# Multi-line comments are joined together. Results are NULL if no description
# could be found.
#
sysrc_desc()
{
local varname="$1"
(
buffer=
while read LINE; do
case "$LINE" in
$varname=*)
buffer="$LINE"
break
esac
done
# Return if the variable wasn't found
[ "$buffer" ] || return $FAILURE
regex='[[:alpha:]_][[:alnum:]_]*='
while read LINE; do
#
# Stop reading comments if we reach a new assignment
# directive or if the line contains only whitespace
#
echo "$LINE" | grep -q "^[[:space:]]*$regex" && break
echo "$LINE" | grep -q "^[[:space:]]*#$regex" && break
echo "$LINE" | grep -q "^[[:space:]]*$" && break
# Append new line to buffer
buffer="$buffer
$LINE"
done
# Return if the buffer is empty
[ "$buffer" ] || return $FAILURE
#
# Clean up the buffer.
#
regex='^[^#]*\(#[[:space:]]*\)\{0,1\}'
buffer="$( echo "$buffer" | sed -e "s/$regex//" )"
buffer="$( echo "$buffer" | tr '\n' ' ' \
| sed -e 's/^[[:space:]]*//;s/[[:space:]]*$//' )"
echo "$buffer"
) < "$RC_DEFAULTS"
}
############################################################ MAIN SOURCE
#
# Perform sanity checks
#
[ $# -gt 0 ] || usage
#
# Process command-line options
#
while getopts hf:aAdevinN flag; do
case "$flag" in
h) usage;;
f) RC_CONFS="$OPTARG";;
a) SHOW_ALL=1;;
A) SHOW_ALL=2;;
d) DESCRIBE=1;;
e) SHOW_EQUALS=1;;
v) SYSRC_VERBOSE=1;;
i) IGNORE_UNKNOWNS=1;;
n) SHOW_NAME=;;
N) SHOW_VALUE=;;
\?) usage;;
esac
done
shift $(( $OPTIND - 1 ))
#
# Process command-line options
#
SEP=': '
[ "$SHOW_EQUALS" ] && SEP='="'
[ "$SHOW_NAME" ] || SHOW_EQUALS=
[ "$SYSRC_VERBOSE" = "0" ] && SYSRC_VERBOSE=
if [ ! "$SHOW_VALUE" ]; then
SHOW_NAME=1
SHOW_EQUALS=
fi
if [ "$SHOW_ALL" ]; then
#
# Get a list of variables that are currently set in the rc.conf(5)
# files (included `/etc/defaults/rc.conf') by performing a call to
# source_rc_confs() in a clean environment.
#
(
#
# Set which variables we want to preserve in the environment.
# Append the pipe-character (|) to the list of internal field
# separation (IFS) characters, allowing us to use the below
# list both as an extended grep (-E) pattern and argument list
# (required to first get clean_env() to preserve these in the
# environment and then later to prune them from the list of
# variables produced by set(1)).
#
IFS="$IFS|"
EXCEPT="IFS|EXCEPT|PATH|RC_DEFAULTS|OPTIND|DESCRIBE|SEP"
EXCEPT="$EXCEPT|SHOW_ALL|SHOW_EQUALS|SHOW_NAME|SHOW_VALUE"
EXCEPT="$EXCEPT|SYSRC_VERBOSE|RC_CONFS"
#
# Clean the environment (except for our required variables)
# and then source the required files.
#
clean_env --except $EXCEPT
if [ -f "$RC_DEFAULTS" -a -r "$RC_DEFAULTS" ]; then
. "$RC_DEFAULTS"
#
# If passed `-a' (rather than `-A'), re-purge the
# environment, removing the rc.conf(5) defaults.
#
[ "$SHOW_ALL" = "1" ] \
&& clean_env --except rc_conf_files $EXCEPT
#
# If `-f file' was passed, set $rc_conf_files to an
# explicit value, modifying the default behavior of
# source_rc_confs().
#
[ "$RC_CONFS" ] && rc_conf_files="$RC_CONFS"
source_rc_confs
#
# If passed `-a' (rather than `-A'), remove
# `rc_conf_files' unless it was defined somewhere
# other than rc.conf(5) defaults.
#
[ "$SHOW_ALL" = "1" -a \
"$( sysrc_find rc_conf_files )" = "$RC_DEFAULTS" \
] \
&& unset rc_conf_files
fi
for NAME in $( set | awk -F= \
'/^[[:alpha:]_][[:alnum:]_]*=/ {print $1}' \
| grep -Ev "^($EXCEPT)$"
); do
#
# If enabled, describe rather than expand value
#
if [ "$DESCRIBE" ]; then
echo "$NAME: $( sysrc_desc "$NAME" )"
continue
fi
[ "$SYSRC_VERBOSE" ] && \
echo -n "$( sysrc_find "$NAME" ): "
#
# If `-N' is passed, simplify the output
#
if [ ! "$SHOW_VALUE" ]; then
echo "$NAME"
continue
fi
echo "${SHOW_NAME:+$NAME$SEP}$(
sysrc_get "$NAME" )${SHOW_EQUALS:+\"}"
done
)
#
# Ignore the remainder of positional arguments.
#
exit $SUCCESS
fi
#
# Process command-line arguments
#
while [ $# -gt 0 ]; do
NAME="${1%%=*}"
[ "$DESCRIBE" ] && \
echo "$NAME: $( sysrc_desc "$NAME" )"
case "$1" in
*=*)
#
# Like sysctl(8), if both `-d' AND "name=value" is passed,
# first describe, then attempt to set
#
if [ "$SYSRC_VERBOSE" ]; then
file="$( sysrc_find "$NAME" )"
[ "$file" = "$RC_DEFAULTS" -o ! "$file" ] && \
file="$( sysrc_get "rc_conf_files%%[$IFS]*" )"
echo -n "$file: "
fi
#
# If `-N' is passed, simplify the output
#
if [ ! "$SHOW_VALUE" ]; then
echo "$NAME"
sysrc_set "$NAME" "${1#*}"
else
echo -n "${SHOW_NAME:+$NAME$SEP}$(
sysrc_get "$NAME" )${SHOW_EQUALS:+\"}"
if sysrc_set "$NAME" "${1#*=}"; then
echo " -> $( sysrc_get "$NAME" )"
fi
fi
;;
*)
if ! IGNORED="$( sysrc_get "$NAME?" )"; then
[ "$IGNORE_UNKNOWNS" ] \
|| echo "$progname: unknown variable '$NAME'"
shift 1
continue
fi
#
# Like sysctl(8), when `-d' is passed,
# desribe it rather than expanding it
#
if [ "$DESCRIBE" ]; then
shift 1
continue
fi
[ "$SYSRC_VERBOSE" ] && \
echo -n "$( sysrc_find "$NAME" ): "
#
# If `-N' is passed, simplify the output
#
if [ ! "$SHOW_VALUE" ]; then
echo "$NAME"
else
echo "${SHOW_NAME:+$NAME$SEP}$(
sysrc_get "$NAME" )${SHOW_EQUALS:+\"}"
fi
esac
shift 1
done
--
Cheers,
Devin Teske
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Business Solutions Consultant II
FIS - fisglobal.com
510-735-5650 Mobile
510-621-2038 Office
510-621-2020 Office Fax
909-477-4578 Home/Fax
devin.teske at fisglobal.com
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