Fatal编程技术网
  • bash/
  • Bash 确保一次只运行一个shell脚本实例的快捷方法

Bash 确保一次只运行一个shell脚本实例的快捷方法

bash shell process

Bash 确保一次只运行一个shell脚本实例的快捷方法,bash,shell,process,lockfile,Bash,Shell,Process,Lockfile,什么是确保在给定时间内只运行一个shell脚本实例的快捷方法？用于在文件描述符上设置独占作用域锁。这样，您甚至可以同步脚本的不同部分 #!/bin/bash ( # Wait for lock on /var/lock/.myscript.exclusivelock (fd 200) for 10 seconds flock -x -w 10 200 || exit 1 # Do stuff ) 200>/var/lock/.myscript.exclusivelock

什么是确保在给定时间内只运行一个shell脚本实例的快捷方法？

用于在文件描述符上设置独占作用域锁。这样，您甚至可以同步脚本的不同部分

#!/bin/bash

(
  # Wait for lock on /var/lock/.myscript.exclusivelock (fd 200) for 10 seconds
  flock -x -w 10 200 || exit 1

  # Do stuff

) 200>/var/lock/.myscript.exclusivelock
这可以确保
（
和
）
之间的代码一次只由一个进程运行，并且该进程不会等待太长的锁

警告：此特定命令是的一部分。如果您运行的操作系统不是Linux，那么它可能可用，也可能不可用。

羊群路径是一条可行之路。想想当剧本突然死亡时会发生什么。在羊群的情况下，你只是失去了羊群，但这不是一个问题。另外，请注意，一个邪恶的伎俩是对脚本本身采取羊群行动。。但这当然会让您在权限问题上全力以赴。

在已知位置创建一个锁文件，并在脚本启动时检查是否存在？如果有人试图跟踪阻止脚本执行的错误实例，则将PID放入文件中可能会有所帮助。

快速而肮脏

#!/bin/bash

(
  # Wait for lock on /var/lock/.myscript.exclusivelock (fd 200) for 10 seconds
  flock -x -w 10 200 || exit 1

  # Do stuff

) 200>/var/lock/.myscript.exclusivelock

#!/bin/sh

if [ -f sometempfile ]
  echo "Already running... will now terminate."
  exit
else
  touch sometempfile
fi

..do what you want here..

rm sometempfile
PID和LockFile绝对是最可靠的。当您尝试运行程序时，它可以检查锁文件，如果它存在，它可以使用
ps
查看进程是否仍在运行。如果没有，脚本可以启动，将锁文件中的PID更新为自己的PID。

下面是一个使用锁文件并向其中回显PID的实现。如果进程在删除pidfile之前被终止，这将起到保护作用：

这里的诀窍是
kill-0
，它不传递任何信号，只检查是否存在具有给定PID的进程。另外，调用
trap
将确保即使进程被终止（除了
kill-9
）时，锁文件也会被删除。

在flock（2）系统调用中有一个包装器，毫无想象力地称为flock（1）。这使得可靠地获得独占锁相对容易，而不必担心清理等问题。关于如何在shell脚本中使用它，有一些示例。

一些unix具有
锁文件
，这与前面提到的
flock
非常相似

从手册页：

lockfile可用于创建一个 一个或多个信号量文件。如果锁定- 文件无法创建所有指定的 文件（按指定的顺序），它 等待睡眠时间（默认为8） 秒，然后重试所创建的最后一个文件 没有成功。您可以指定 要执行的重试次数，直到 返回失败。如果号码是 重试次数为-1（默认值，即。， -r-1）锁定文件将永远重试

要使锁定可靠，您需要原子操作。上述许多建议 它们不是原子的。建议的lockfile（1）实用程序看起来很有希望成为手册页 提到它的“抗NFS”。如果您的操作系统不支持锁文件（1）和 您的解决方案必须在NFS上运行，您没有太多的选项

NFSv2有两个原子操作：

  • 符号链接
  • 改名
对于NFSv3，创建调用也是原子的

目录操作在NFSv2和NFSv3下不是原子的（请参阅Brent Callaghan的《NFS图解》一书，ISBN 0-201-32570-5；Brent是Sun的NFS老手）

知道了这一点，您可以为文件和目录实现旋转锁（在shell中，而不是在PHP中）：

锁定当前目录：

while ! ln -s . lock; do :; done
锁定文件：

while ! ln -s ${f} ${f}.lock; do :; done
解锁当前目录（假设，正在运行的进程确实获得了锁）：

解锁文件（假设正在运行的进程确实获得了锁）：

Remove也不是原子的，因此首先是重命名（原子的），然后是Remove

对于symlink和rename调用，两个文件名必须驻留在同一个文件系统上。我的建议是：只使用简单的文件名（没有路径），将文件和锁放在同一个目录中。

所有测试“锁文件”存在性的方法都有缺陷

为什么?？因为无法检查文件是否存在并在单个原子操作中创建它。因此,；有一种竞赛条件，将使你的互斥尝试中断

相反，您需要使用
mkdir
mkdir
如果目录尚不存在，则创建一个目录，如果存在，则设置退出代码。更重要的是，它在一个原子动作中完成了所有这一切，使它非常适合这种场景

if ! mkdir /tmp/myscript.lock 2>/dev/null; then
    echo "Myscript is already running." >&2
    exit 1
fi
有关所有详细信息，请参阅优秀的BashFAQ：

如果你想处理陈旧的锁，它会派上用场。这里唯一的缺点是操作需要大约一秒钟的时间，因此它不是即时的

下面是我曾经编写的一个函数，它使用fuser解决了这个问题：

#       mutex file
#
# Open a mutual exclusion lock on the file, unless another process already owns one.
#
# If the file is already locked by another process, the operation fails.
# This function defines a lock on a file as having a file descriptor open to the file.
# This function uses FD 9 to open a lock on the file.  To release the lock, close FD 9:
# exec 9>&-
#
mutex() {
    local file=$1 pid pids 

    exec 9>>"$file"
    { pids=$(fuser -f "$file"); } 2>&- 9>&- 
    for pid in $pids; do
        [[ $pid = $$ ]] && continue

        exec 9>&- 
        return 1 # Locked by a pid.
    done 
}
您可以在这样的脚本中使用它：

mutex /var/run/myscript.lock || { echo "Already running." >&2; exit 1; }
如果您不关心可移植性（这些解决方案应该适用于几乎任何UNIX设备），Linux’提供了一些附加选项，而且还有。

当针对Debian机器时，我发现
lockfile progs
包是一个很好的解决方案
procmail
还附带了一个
lockfile
工具。然而，有时这两个问题我都没有解决

下面是我的解决方案，它使用
mkdir
实现原子性，并使用一个PID文件检测过时的锁。这段代码目前正在Cygwin安装程序中生产，并且运行良好

要使用它，只需在需要独占访问某些内容时调用
exclusive\u lock\u require
。可选的lock name参数允许您在不同脚本之间共享锁。如果您需要更复杂的功能，还有两个较低级别的功能（
exclusive\u lock\u try
和
exclusive\u lock\u retry
）

function exclusive_lock_try() # [lockname]
{

    local LOCK_NAME="${1:-`basename $0`}"

    LOCK_DIR="/tmp/.${LOCK_NAME}.lock"
    local LOCK_PID_FILE="${LOCK_DIR}/${LOCK_NAME}.pid"

    if [ -e "$LOCK_DIR" ]
    then
        local LOCK_PID="`cat "$LOCK_PID_FILE" 2> /dev/null`"
        if [ ! -z "$LOCK_PID" ] && kill -0 "$LOCK_PID" 2> /dev/null
        then
            # locked by non-dead process
            echo "\"$LOCK_NAME\" lock currently held by PID $LOCK_PID"
            return 1
        else
            # orphaned lock, take it over
            ( echo $$ > "$LOCK_PID_FILE" ) 2> /dev/null && local LOCK_PID="$$"
        fi
    fi
    if [ "`trap -p EXIT`" != "" ]
    then
        # already have an EXIT trap
        echo "Cannot get lock, already have an EXIT trap"
        return 1
    fi
    if [ "$LOCK_PID" != "$$" ] &&
        ! ( umask 077 && mkdir "$LOCK_DIR" && umask 177 && echo $$ > "$LOCK_PID_FILE" ) 2> /dev/null
    then
        local LOCK_PID="`cat "$LOCK_PID_FILE" 2> /dev/null`"
        # unable to acquire lock, new process got in first
        echo "\"$LOCK_NAME\" lock currently held by PID $LOCK_PID"
        return 1
    fi
    trap "/bin/rm -rf \"$LOCK_DIR\"; exit;" EXIT

    return 0 # got lock

}

function exclusive_lock_retry() # [lockname] [retries] [delay]
{

    local LOCK_NAME="$1"
    local MAX_TRIES="${2:-5}"
    local DELAY="${3:-2}"

    local TRIES=0
    local LOCK_RETVAL

    while [ "$TRIES" -lt "$MAX_TRIES" ]
    do

        if [ "$TRIES" -gt 0 ]
        then
            sleep "$DELAY"
        fi
        local TRIES=$(( $TRIES + 1 ))

        if [ "$TRIES" -lt "$MAX_TRIES" ]
        then
            exclusive_lock_try "$LOCK_NAME" > /dev/null
        else
            exclusive_lock_try "$LOCK_NAME"
        fi
        LOCK_RETVAL="${PIPESTATUS[0]}"

        if [ "$LOCK_RETVAL" -eq 0 ]
        then
            return 0
        fi

    done

    return "$LOCK_RETVAL"

}

function exclusive_lock_require() # [lockname] [retries] [delay]
{
    if ! exclusive_lock_retry "$@"
    then
        exit 1
    fi
}
你需要像flock一样的原子操作，否则这最终会失败

但是，如果找不到flock，该怎么办呢。嗯，有mkdir。这也是一个原子操作。只有 
mutex /var/run/myscript.lock || { echo "Already running." >&2; exit 1; }

function exclusive_lock_try() # [lockname]
{

    local LOCK_NAME="${1:-`basename $0`}"

    LOCK_DIR="/tmp/.${LOCK_NAME}.lock"
    local LOCK_PID_FILE="${LOCK_DIR}/${LOCK_NAME}.pid"

    if [ -e "$LOCK_DIR" ]
    then
        local LOCK_PID="`cat "$LOCK_PID_FILE" 2> /dev/null`"
        if [ ! -z "$LOCK_PID" ] && kill -0 "$LOCK_PID" 2> /dev/null
        then
            # locked by non-dead process
            echo "\"$LOCK_NAME\" lock currently held by PID $LOCK_PID"
            return 1
        else
            # orphaned lock, take it over
            ( echo $$ > "$LOCK_PID_FILE" ) 2> /dev/null && local LOCK_PID="$$"
        fi
    fi
    if [ "`trap -p EXIT`" != "" ]
    then
        # already have an EXIT trap
        echo "Cannot get lock, already have an EXIT trap"
        return 1
    fi
    if [ "$LOCK_PID" != "$$" ] &&
        ! ( umask 077 && mkdir "$LOCK_DIR" && umask 177 && echo $$ > "$LOCK_PID_FILE" ) 2> /dev/null
    then
        local LOCK_PID="`cat "$LOCK_PID_FILE" 2> /dev/null`"
        # unable to acquire lock, new process got in first
        echo "\"$LOCK_NAME\" lock currently held by PID $LOCK_PID"
        return 1
    fi
    trap "/bin/rm -rf \"$LOCK_DIR\"; exit;" EXIT

    return 0 # got lock

}

function exclusive_lock_retry() # [lockname] [retries] [delay]
{

    local LOCK_NAME="$1"
    local MAX_TRIES="${2:-5}"
    local DELAY="${3:-2}"

    local TRIES=0
    local LOCK_RETVAL

    while [ "$TRIES" -lt "$MAX_TRIES" ]
    do

        if [ "$TRIES" -gt 0 ]
        then
            sleep "$DELAY"
        fi
        local TRIES=$(( $TRIES + 1 ))

        if [ "$TRIES" -lt "$MAX_TRIES" ]
        then
            exclusive_lock_try "$LOCK_NAME" > /dev/null
        else
            exclusive_lock_try "$LOCK_NAME"
        fi
        LOCK_RETVAL="${PIPESTATUS[0]}"

        if [ "$LOCK_RETVAL" -eq 0 ]
        then
            return 0
        fi

    done

    return "$LOCK_RETVAL"

}

function exclusive_lock_require() # [lockname] [retries] [delay]
{
    if ! exclusive_lock_retry "$@"
    then
        exit 1
    fi
}

if mkdir /var/lock/.myscript.exclusivelock
then
  # do stuff
  :
  rmdir /var/lock/.myscript.exclusivelock
fi

## Test the lock
LOCKFILE=/tmp/singleton.lock 
if [ -e ${LOCKFILE} ] && kill -0 `cat ${LOCKFILE}`; then
    echo "Script already running. bye!"
    exit 
fi

## Set the lock 
echo $$ > ${LOCKFILE}

set -C
lockfile="/tmp/locktest.lock"
if echo "$$" > "$lockfile"; then
    echo "Successfully acquired lock"
    # do work
    rm "$lockfile"    # XXX or via trap - see below
else
    echo "Cannot acquire lock - already locked by $(cat "$lockfile")"
fi

open(pathname, O_CREAT|O_EXCL)

$ strace -e trace=creat,open -f /bin/bash /home/mikel/bin/testopen 2>&1 | grep -F testopen.lock
open("/tmp/testopen.lock", O_WRONLY|O_CREAT|O_EXCL|O_LARGEFILE, 0666) = 3

$ strace -e trace=creat,open -f /bin/zsh /home/mikel/bin/testopen 2>&1 | grep -F testopen.lock
open("/tmp/testopen.lock", O_WRONLY|O_CREAT|O_EXCL|O_NOCTTY|O_LARGEFILE, 0666) = 3

$ strace -e trace=creat,open -f /bin/pdksh /home/mikel/bin/testopen 2>&1 | grep -F testopen.lock
open("/tmp/testopen.lock", O_WRONLY|O_CREAT|O_EXCL|O_TRUNC|O_LARGEFILE, 0666) = 3

$ strace -e trace=creat,open -f /bin/dash /home/mikel/bin/testopen 2>&1 | grep -F testopen.lock
open("/tmp/testopen.lock", O_WRONLY|O_CREAT|O_EXCL|O_LARGEFILE, 0666) = 3

# acquire lock
# do work (code here may call exit, etc.)
rm "$lockfile"

trap 'rm "$lockfile"' EXIT

#=======================================================================
# Predefined Global Variables
#=======================================================================

TMPDIR=/tmp/myapp
[[ ! -d $TMP_DIR ]] \
    && mkdir -p $TMP_DIR \
    && chmod 700 $TMPDIR

LOCK_DIR=$TMP_DIR/lock

#=======================================================================
# Functions
#=======================================================================

function mklock {
    __lockdir="$LOCK_DIR/$(date +%s.%N).$$" # Private Global. Use Epoch.Nano.PID

    # If it can create $LOCK_DIR then no other instance is running
    if $(mkdir $LOCK_DIR)
    then
        mkdir $__lockdir  # create this instance's specific lock in queue
        LOCK_EXISTS=true  # Global
    else
        echo "FATAL: Lock already exists. Another copy is running or manually lock clean up required."
        exit 1001  # Or work out some sleep_while_execution_lock elsewhere
    fi
}

function rmlock {
    [[ ! -d $__lockdir ]] \
        && echo "WARNING: Lock is missing. $__lockdir does not exist" \
        || rmdir $__lockdir
}

#-----------------------------------------------------------------------
# Private Signal Traps Functions {{{2
#
# DANGER: SIGKILL cannot be trapped. So, try not to `kill -9 PID` or 
#         there will be *NO CLEAN UP*. You'll have to manually remove 
#         any locks in place.
#-----------------------------------------------------------------------
function __sig_exit {

    # Place your clean up logic here 

    # Remove the LOCK
    [[ -n $LOCK_EXISTS ]] && rmlock
}

function __sig_int {
    echo "WARNING: SIGINT caught"    
    exit 1002
}

function __sig_quit {
    echo "SIGQUIT caught"
    exit 1003
}

function __sig_term {
    echo "WARNING: SIGTERM caught"    
    exit 1015
}

#=======================================================================
# Main
#=======================================================================

# Set TRAPs
trap __sig_exit EXIT    # SIGEXIT
trap __sig_int INT      # SIGINT
trap __sig_quit QUIT    # SIGQUIT
trap __sig_term TERM    # SIGTERM

mklock

# CODE

exit # No need for cleanup code here being in the __sig_exit trap function

#!/bin/bash

{
    # exit if we are unable to obtain a lock; this would happen if 
    # the script is already running elsewhere
    # note: -x (exclusive) is the default
    flock -n 100 || exit

    # put commands to run here
    sleep 100
} 100>/tmp/myjob.lock 

lockfile=/var/lock/myscript.lock

if ( set -o noclobber; echo "$$" > "$lockfile") 2> /dev/null ; then
  trap 'rm -f "$lockfile"; exit $?' INT TERM EXIT
else
  # or you can decide to skip the "else" part if you want
  echo "Another instance is already running!"
fi

   #!/bin/bash
   #set -e this is useful only for very stupid scripts because script fails when anything command exits with status more than 0 !! without possibility for capture exit codes. not all commands exits >0 are failed.

( #start subprocess
  # Wait for lock on /var/lock/.myscript.exclusivelock (fd 200) for 10 seconds
  flock -x -w 10 200
  if [ "$?" != "0" ]; then echo Cannot lock!; exit 1; fi
  echo $$>>/var/lock/.myscript.exclusivelock #for backward lockdir compatibility, notice this command is executed AFTER command bottom  ) 200>/var/lock/.myscript.exclusivelock.
  # Do stuff
  # you can properly manage exit codes with multiple command and process algorithm.
  # I suggest throw this all to external procedure than can properly handle exit X commands

) 200>/var/lock/.myscript.exclusivelock   #exit subprocess

FLOCKEXIT=$?  #save exitcode status
    #do some finish commands

exit $FLOCKEXIT   #return properly exitcode, may be usefull inside external scripts

[[ $(pgrep -c "`basename \"$0\"`") -gt 1 ]] && exit

#!/usr/bin/env sh
# Author: rouble

LOCKFILE=/var/tmp/lockfile #customize this line

trap release INT TERM EXIT

# Creates a lockfile. Sets global variable $ACQUIRED to true on success.
# 
# Returns 0 if it is successfully able to create lockfile.
acquire () {
    set -C #Shell noclobber option. If file exists, > will fail.
    UUID=`ps -eo pid,ppid,lstart $$ | tail -1`
    if (echo "$UUID" > "$LOCKFILE") 2>/dev/null; then
        ACQUIRED="TRUE"
        return 0
    else
        if [ -e $LOCKFILE ]; then 
            # We may be dealing with a stale lock file.
            # Bring out the magnifying glass. 
            CURRENT_UUID_FROM_LOCKFILE=`cat $LOCKFILE`
            CURRENT_PID_FROM_LOCKFILE=`cat $LOCKFILE | cut -f 1 -d " "`
            CURRENT_UUID_FROM_PS=`ps -eo pid,ppid,lstart $CURRENT_PID_FROM_LOCKFILE | tail -1`
            if [ "$CURRENT_UUID_FROM_LOCKFILE" == "$CURRENT_UUID_FROM_PS" ]; then 
                echo "Script already running with following identification: $CURRENT_UUID_FROM_LOCKFILE" >&2
                return 1
            else
                # The process that created this lock file died an ungraceful death. 
                # Take ownership of the lock file.
                echo "The process $CURRENT_UUID_FROM_LOCKFILE is no longer around. Taking ownership of $LOCKFILE"
                release "FORCE"
                if (echo "$UUID" > "$LOCKFILE") 2>/dev/null; then
                    ACQUIRED="TRUE"
                    return 0
                else
                    echo "Cannot write to $LOCKFILE. Error." >&2
                    return 1
                fi
            fi
        else
            echo "Do you have write permissons to $LOCKFILE ?" >&2
            return 1
        fi
    fi
}

# Removes the lock file only if this script created it ($ACQUIRED is set), 
# OR, if we are removing a stale lock file (first parameter is "FORCE") 
release () {
    #Destroy lock file. Take no prisoners.
    if [ "$ACQUIRED" ] || [ "$1" == "FORCE" ]; then
        rm -f $LOCKFILE
    fi
}

# Test code
# int main( int argc, const char* argv[] )
echo "Acquring lock."
acquire
if [ $? -eq 0 ]; then 
    echo "Acquired lock."
    read -p "Press [Enter] key to release lock..."
    release
    echo "Released lock."
else
    echo "Unable to acquire lock."
fi

[ "${FLOCKER}" != "$0" ] && exec env FLOCKER="$0" flock -en "$0" "$0" "$@" || :

[ "${FLOCKER}" != "$0" ] && { echo "Trying to start build from queue... "; exec bash -c "FLOCKER='$0' flock -E $E_LOCKED -en '$0' '$0' '$@' || if [ \"\$?\" -eq $E_LOCKED ]; then echo 'Locked.'; fi"; } || echo "Lock is free. Completing."

#!/bin/dash

SCRIPTNAME=$(basename $0)
LOCKDIR="/var/lock/${SCRIPTNAME}"
PIDFILE="${LOCKDIR}/pid"

if ! mkdir $LOCKDIR 2>/dev/null
then
    # lock failed, but check for stale one by checking if the PID is really existing
    PID=$(cat $PIDFILE)
    if ! kill -0 $PID 2>/dev/null
    then
       echo "Removing stale lock of nonexistent PID ${PID}" >&2
       rm -rf $LOCKDIR
       echo "Restarting myself (${SCRIPTNAME})" >&2
       exec "$0" "$@"
    fi
    echo "$SCRIPTNAME is already running, bailing out" >&2
    exit 1
else
    # lock successfully acquired, save PID
    echo $$ > $PIDFILE
fi

trap "rm -rf ${LOCKDIR}" QUIT INT TERM EXIT


echo hello

sleep 30s

echo bye

sem --id SCRIPTSINGLETON yourScript

sem --id SCRIPTSINGLETON --semaphoretimeout -10 yourScript

if [[ $(ps axf | awk -v pid=$$ '$1!=pid && $6~/'$(basename $0)'/{print $1}') ]]; then echo "Already running"; exit; fi

obtain_lock()
{
  LOCK="${1}"
  LOCKDIR="$(dirname "${LOCK}")"
  LOCKFILE="$(basename "${LOCK}")"

  # create temp lock file
  TMPLOCK=$(mktemp -p "${LOCKDIR}" "${LOCKFILE}XXXXXX" 2> /dev/null)
  if test "x${TMPLOCK}" == "x";then
     echo "unable to create temporary file with mktemp" 1>&2
     return 1
  fi
  echo "$$" > "${TMPLOCK}"

  # attempt to obtain lock file
  ln "${TMPLOCK}" "${LOCK}" 2> /dev/null
  if test $? -ne 0;then
     rm -f "${TMPLOCK}"
     echo "unable to obtain lockfile" 1>&2
     if test -f "${LOCK}";then
        echo "current lock information held by: $(cat "${LOCK}")" 1>&2
     fi
     return 2
  fi
  rm -f "${TMPLOCK}"

  return 0;
};

#!/bin/sh

. /path/to/locking/profile.sh
PROG_LOCKFILE="/tmp/myprog.lock"

clean_up()
{
  rm -f "${PROG_LOCKFILE}"
}

obtain_lock "${PROG_LOCKFILE}"
if test $? -ne 0;then
   exit 1
fi
trap clean_up SIGHUP SIGINT SIGTERM

# bulk of script

clean_up
exit 0
# end of script

#!/bin/bash

exec 9<> /tmp/foo
flock -n 9
RET=$?
if [[ $RET -ne 0 ]] ; then
    echo "lock failed, exiting"
    exit
fi

#Now we are inside the "critical section"
echo "inside lock"
sleep 5
exec 9>&- #close fd 9, and release lock

#The part below is outside the critical section (the lock)
echo "lock released"
sleep 5

LOCK_FILE="/var/lock/$(basename "$0").pid"
trap "rm -f ${LOCK_FILE}; exit" INT TERM EXIT
if [[ -f $LOCK_FILE && -d /proc/`cat $LOCK_FILE` ]]; then
   // Process already exists
   exit 1
fi
echo $$ > $LOCK_FILE

lock_file=/tmp/`basename $0`.lock

if fuser $lock_file > /dev/null 2>&1; then
    echo "WARNING: Other instance of $(basename $0) running."
    exit 1
fi
exec 3> $lock_file 

#!/bin/bash

if [[ $(pgrep -afc "$(basename "$0")") -gt "1" ]]; then echo "Another instance of "$0" has already been started!" && exit; fi
.
the_beginning_of_actual_script