io-set-sched

#!/bin/bash

###########################################################################
#
#  Copyright (c) 2018 Timothy Savannah All Rights Reserved
#
#    Licensed under terms of the GNU General Public License Version 3
#     which should have been supplied with this distribution as LICENSE
#
#    If not, you can access the latest LICENSE at:
#      https://raw.githubusercontent.com/kata198/ioschedset/master/LICENSE
#
#
#  io-set-sched - Alters the current I/O scheduler for block devices
#
###########################################################################

PROG_NAME="${BASH_SOURCE[0]}"
PROG_PATH="$(realpath "$0")"
PROG_BASENAME="$(basename "${PROG_PATH}")"

VERSION="1.1.1"

get_available_schedulers() {
    pushd /sys/block >/dev/null 2>&1
    FIRST_BLOCK_DEVICE="$(echo * | tr ' ' '\n' | head -n1)"
    popd >/dev/null 2>&1

    AVAILABLE_SCHEDULERS="$(cat "/sys/block/${FIRST_BLOCK_DEVICE}/queue/scheduler" | sed -e 's|\[||g' -e 's|\]||g')"
    
    echo "${AVAILABLE_SCHEDULERS}"
}

usage() {
    AVAILABLE_SCHEDULERS="$(get_available_schedulers)"

    cat 2>&1 <<EOT 
Usage: ${PROG_BASENAME} [scheduler] ([block device name1] ... [block device nameN])
  Sets the IO scheduler for block devices

If no arguments are provided, will set for all devices.
  Otherwise, will apply to every block device listed

You may also call: \`${PROG_BASENAME} --list'
  to list available schedulers.

Choice of schedulers: ${AVAILABLE_SCHEDULERS}

${PROG_BASENAME} version ${VERSION} by Timothy Savannah
EOT

}

cd /sys/block

if [ $# -eq 0 ];
then
    printf "Not enough arguments.\n\n" >&2
    usage
    exit 1;
fi

for arg in "$@";
do
    if [[ "${arg}" = '--help' ]];
    then
        usage;
        exit 1;
    elif [[ "${arg}" = '--list' ]];
    then
        AVAILABLE_SCHEDULERS="$(get_available_schedulers)"
        printf "%s\n" "${AVAILABLE_SCHEDULERS}"
        exit 0;
    elif [[ "${arg}" = "--version" ]];
    then
        printf "\n${PROG_BASENAME} version ${VERSION} by Timothy Savannah\n\n" >&2
        exit 0;
    fi
    
done

# Do this AFTER the arg parsing, we don't need to be root to read the usage
#  nor to query available scheulers
if [ "`whoami`" != "root" ];
then
    printf "Must be root to set IO Scheduler. Rerunning under sudo...\n\n" >&2
    sudo "${PROG_PATH}" "$@"
    exit $?
fi


IO_SCHED="$1"
shift

if [ $# -eq 0 ];
then
    # No args after io scheduler, apply to all
    BLOCK_DEVS="$(echo *)"
else
    # Otherwise, apply only to specified devices
    BLOCK_DEVS="$@"
fi

exitCode=0

for blockDev in ${BLOCK_DEVS};
do
    # Incase we got passed /dev/sda or whatever, do the basename
    blockDev="$(basename "${blockDev}")"
    if [ ! -d "${blockDev}" ];
    then
        printf "No such block device: '%s'.\n\tRun \`io-get-sched' without agruments for a list of all devices\n" "${blockDev}" >&2
        # set exit code to ENOENT ( No Such File or Directory )
        exitCode=2
        continue
    fi
    echo "${IO_SCHED}" > "./${blockDev}/queue/scheduler"
    RET=$?
    if [ $RET -eq 0 ];
    then
        printf "+ Successfully set %s to '%s'!\n" "${blockDev}" "${IO_SCHED}"
    else
        printf "%s FAILED to set %s to '%s' [%d]!\n" '--' "${blockDev}" "${IO_SCHED}" "${RET}"
        exitCode=${RET}
    fi

done


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