保存并恢复陷阱状态?管理多个陷阱处理程序的简便方法?

时间:2013-04-20 00:08:44

标签: arrays bash stack bash-trap

什么是覆盖bash陷阱处理程序的好方法,这些陷阱处理程序不会永久地删除可能已经设置或可能尚未设置的现有陷阱处理程序?如何动态管理陷阱例程的任意链?

有没有办法保存陷阱处理程序的当前状态,以便以后可以恢复?

1 个答案:

答案 0 :(得分:16)

在Bash中保存并恢复陷阱处理程序状态

我会提交以下堆栈实现来跟踪和恢复陷阱状态。使用这种方法,我可以推动陷阱更改,然后在我完成它们时将它们弹出。这也可以用来将许多陷阱例程链接在一起。

请参阅以下源文件(.trap_stack.sh)

#!/bin/bash
trap_stack_name() {
  local sig=${1//[^a-zA-Z0-9]/_}
  echo "__trap_stack_$sig"
}

extract_trap() {
  echo ${@:3:$(($#-3))}
}

get_trap() {
  eval echo $(extract_trap `trap -p $1`)
}

trap_push() {
  local new_trap=$1
  shift
  local sigs=$*
  for sig in $sigs; do
    local stack_name=`trap_stack_name "$sig"`
    local old_trap=$(get_trap $sig)
    eval "${stack_name}"'[${#'"${stack_name}"'[@]}]=$old_trap'
    trap "${new_trap}" "$sig"
  done
}

trap_pop() {
  local sigs=$*
  for sig in $sigs; do
    local stack_name=`trap_stack_name "$sig"`
    local count; eval 'count=${#'"${stack_name}"'[@]}'
    [[ $count -lt 1 ]] && return 127
    local new_trap
    local ref="${stack_name}"'[${#'"${stack_name}"'[@]}-1]'
    local cmd='new_trap=${'"$ref}"; eval $cmd
    trap "${new_trap}" "$sig"
    eval "unset $ref"
  done
}

trap_prepend() {
  local new_trap=$1
  shift
  local sigs=$*
  for sig in $sigs; do
    if [[ -z $(get_trap $sig) ]]; then
      trap_push "$new_trap" "$sig"
    else
      trap_push "$new_trap ; $(get_trap $sig)" "$sig"
    fi
  done
}

trap_append() {
  local new_trap=$1
  shift
  local sigs=$*
  for sig in $sigs; do
    if [[ -z $(get_trap $sig) ]]; then
      trap_push "$new_trap" "$sig"
    else
      trap_push "$(get_trap $sig) ; $new_trap" "$sig"
    fi
  done
}

这可以管理定义为命名函数的处理程序以及定义为此示例trap "kill $!" SIGTERM SIGINT的临时例程。

这是我用来帮助我编写的测试脚本:

#!/bin/bash
source .trap_stack.sh

initial_trap='echo "messy" ;'" echo 'handler'"
non_f_trap='echo "non-function trap"'
f_trap() {
  echo "function trap"
}

print_status() {
  echo "    SIGINT  trap: `get_trap SIGINT`"  
  echo "    SIGTERM trap: `get_trap SIGTERM`"
  echo "-------------"
  echo
}

echo "--- TEST START ---"
echo "Initial trap state (should be empty):"
print_status

echo 'Setting messy non-function handler for SIGINT ("original state")'
trap "$initial_trap" SIGINT
print_status

echo 'Pop empty stacks (still in original state)'
trap_pop SIGINT SIGTERM
print_status

echo 'Push non-function handler for SIGINT'
trap_push "$non_f_trap" SIGINT
print_status

echo 'Append function handler for SIGINT and SIGTERM'
trap_append f_trap SIGINT SIGTERM
print_status

echo 'Prepend function handler for SIGINT and SIGTERM'
trap_prepend f_trap SIGINT SIGTERM
print_status

echo 'Push non-function handler for SIGINT and SIGTERM'
trap_push "$non_f_trap" SIGINT SIGTERM
print_status

echo 'Pop both stacks'
trap_pop SIGINT SIGTERM
print_status

echo 'Prepend function handler for SIGINT and SIGTERM'
trap_prepend f_trap SIGINT SIGTERM
print_status

echo 'Pop both stacks thrice'
trap_pop SIGINT SIGTERM
trap_pop SIGINT SIGTERM
trap_pop SIGINT SIGTERM
print_status

echo 'Push non-function handler for SIGTERM'
trap_push "$non_f_trap" SIGTERM
print_status

echo 'Pop handler state for SIGINT (SIGINT is now back to original state)'
trap_pop SIGINT
print_status

echo 'Pop handler state for SIGTERM (SIGTERM is now back to original state)'
trap_pop SIGTERM
print_status