我需要这个，但目标进程不是当前shell的子进程，在这种情况下，等待$PID不起作用。我确实找到了以下替代方案:

while [ -e /proc/$PID ]; do sleep 0.1 ; done

这依赖于procfs的存在，它可能不可用(例如Mac不提供它)。所以对于可移植性，你可以用这个代替:

while ps -p $PID >/dev/null ; do sleep 0.1 ; done

正是为了这个目的，我写了一个bash函数:for。

注意::for不仅保留并返回失败函数的退出码，而且终止所有并行运行的实例。在这种情况下可能不需要。

#!/usr/bin/env bash

# Wait for pids to terminate. If one pid exits with
# a non zero exit code, send the TERM signal to all
# processes and retain that exit code
#
# usage:
# :wait 123 32
function :wait(){
    local pids=("$@")
    [ ${#pids} -eq 0 ] && return $?

    trap 'kill -INT "${pids[@]}" &>/dev/null || true; trap - INT' INT
    trap 'kill -TERM "${pids[@]}" &>/dev/null || true; trap - RETURN TERM' RETURN TERM

    for pid in "${pids[@]}"; do
        wait "${pid}" || return $?
    done

    trap - INT RETURN TERM
}

# Run a function in parallel for each argument.
# Stop all instances if one exits with a non zero
# exit code
#
# usage:
# :for func 1 2 3
#
# env:
# FOR_PARALLEL: Max functions running in parallel
function :for(){
    local f="${1}" && shift

    local i=0
    local pids=()
    for arg in "$@"; do
        ( ${f} "${arg}" ) &
        pids+=("$!")
        if [ ! -z ${FOR_PARALLEL+x} ]; then
            (( i=(i+1)%${FOR_PARALLEL} ))
            if (( i==0 )) ;then
                :wait "${pids[@]}" || return $?
                pids=()
            fi
        fi
    done && [ ${#pids} -eq 0 ] || :wait "${pids[@]}" || return $?
}

使用

for.sh:

#!/usr/bin/env bash
set -e

# import :for from gist: https://gist.github.com/Enteee/c8c11d46a95568be4d331ba58a702b62#file-for
# if you don't like curl imports, source the actual file here.
source <(curl -Ls https://gist.githubusercontent.com/Enteee/c8c11d46a95568be4d331ba58a702b62/raw/)

msg="You should see this three times"

:(){
  i="${1}" && shift

  echo "${msg}"

  sleep 1
  if   [ "$i" == "1" ]; then sleep 1
  elif [ "$i" == "2" ]; then false
  elif [ "$i" == "3" ]; then
    sleep 3
    echo "You should never see this"
  fi
} && :for : 1 2 3 || exit $?

echo "You should never see this"

$ ./for.sh; echo $?
You should see this three times
You should see this three times
You should see this three times
1

参考文献

[1]:博客 [2]:要点

我需要这个，但目标进程不是当前shell的子进程，在这种情况下，等待$PID不起作用。我确实找到了以下替代方案:

while [ -e /proc/$PID ]; do sleep 0.1 ; done

这依赖于procfs的存在，它可能不可用(例如Mac不提供它)。所以对于可移植性，你可以用这个代替:

while ps -p $PID >/dev/null ; do sleep 0.1 ; done

为了将此并行化…

for i in $(whatever_list) ; do
   do_something $i
done

翻译成这样…

for i in $(whatever_list) ; do echo $i ; done | ## execute in parallel...
   (
   export -f do_something ## export functions (if needed)
   export PATH ## export any variables that are required
   xargs -I{} --max-procs 0 bash -c ' ## process in batches...
      {
      echo "processing {}" ## optional
      do_something {}
      }' 
   )

If an error occurs in one process, it won't interrupt the other processes, but it will result in a non-zero exit code from the sequence as a whole. Exporting functions and variables may or may not be necessary, in any particular case. You can set --max-procs based on how much parallelism you want (0 means "all at once"). GNU Parallel offers some additional features when used in place of xargs -- but it isn't always installed by default. The for loop isn't strictly necessary in this example since echo $i is basically just regenerating the output of $(whatever_list). I just think the use of the for keyword makes it a little easier to see what is going on. Bash string handling can be confusing -- I have found that using single quotes works best for wrapping non-trivial scripts. You can easily interrupt the entire operation (using ^C or similar), unlike the the more direct approach to Bash parallelism.

下面是一个简化的工作示例……

for i in {0..5} ; do echo $i ; done |xargs -I{} --max-procs 2 bash -c '
   {
   echo sleep {}
   sleep 2s
   }'

wait还(可选地)接受要等待的进程的PID，并且使用$!你会得到最后一个命令的PID在后台启动。 修改循环，将每个衍生子进程的PID存储到一个数组中，然后再次循环等待每个PID。

# run processes and store pids in array
for i in $n_procs; do
    ./procs[${i}] &
    pids[${i}]=$!
done

# wait for all pids
for pid in ${pids[*]}; do
    wait $pid
done

如果你安装了GNU Parallel，你可以这样做:

# If doCalculations is a function
export -f doCalculations
seq 0 9 | parallel doCalculations {}

GNU Parallel会给你退出代码:

0 -所有作业运行无错误。 1-253 -部分作业失败。退出状态给出了失败作业的数量 254—超过253个作业失败。 255 -其他错误。

观看介绍视频了解更多信息:http://pi.dk/1