写入输出流并从 shell 脚本函数返回值

Question

在 shell 脚本中，echo 可用于从函数返回值。 但是，如果这些函数想要打印一些消息。 然后，这可以通过将其重定向到错误流来完成。 下面是一个简化的例子：-

#this is a function that returns a value, as well as
#print some messages
function logic(){
    echo >&2 "start of logic"
    echo >&2 "perform logic, to get value"

    echo "ok"
}

function smain(){
    local result=$(logic)

    echo "result is >$result<"

    if [ "$result" == "ok" ];then
        echo "script successful"
    else
        echo "script failed"
    fi
}

smain

以下是示例执行输出：-

sh sample.sh
start of logic
perform logic, to get value
result is >ok<
script successful

效果很好。 但是当此脚本用作 autosys 作业时。 然后来自逻辑函数的消息最终会出现在触发警报的错误流文件中。

有什么办法，可以将来自逻辑函数的消息写入输出流，而不是将消息与返回值混合。

---

编辑 1：-

#!/usr/bin/env bash

function Return(){
    printf -v "$1" '%s' '$*'
}

function logic() {
    local arg=$1
    local system=$2
    echo "start of logic"
    echo "all params are >$*<"
    echo "perform logic, to get value"
    echo >&2 "logic successfully completed"
    printf -v "$1" '%s' 'abraKaDabra'
}

function main() {
    local result='' ;  logic "$@" result

    printf 'result is >%s<\n' "$result"

    if [ "$result" = "ok" ]; then
        echo "script successful"
    else
        echo "script failed"
    fi

    echo >&2 "end of main"
}

main "$@"

输出：-

$

sh returnValueWithDebugging.sh abc xyz > out.log 2>err.log

$

cat err.log
logic successfully completed
end of main

$

cat out.log
start of logic
all params are >abc xyz result<
perform logic, to get value
result is ><
script failed

Answer 1

这行得通吗？：

#this is a function that returns a value, as well as                            
#print some messages                                                            
function logic(){
    echo "start of logic"
    echo "perform logic, to get value"

    echo "ok" >&2
}

function smain(){
    { local result=$( { { logic ; } 1>&3 ; } 2>&1); } 3>&1

    echo "result is >$result<"

    if [ "$result" == "ok" ];then
        echo "script successful"
    else
        echo "script failed"
    fi
}

smain

Answer 2

如果函数的返回是一个简单的状态指示符（如正常或失败），我建议您使用返回码。

由于您将问题标记为 Bash，因此可以通过引用而不是使用输出流来返回任意值，其优点是不在子 shell 进程中调用您的函数：

将返回值作为引用传递（结果变量名作为参数 1 传递）：

#!/usr/bin/env bash
logic()
{
  echo "start of logic"
  echo "perform logic, to get value"
  printf -v "$1" '%s' 'ok'
}

function main ()
{
  result=''
  logic result

  printf 'result is >%s<\n' "$result"

  if [ "$result" = "ok" ];then
    echo "script successful"
  else
    echo "script failed"
  fi
}

main "$@"

或者，您可以将 name-ref 变量与 declare -n 一起使用，并将 logic 函数编写为：

logic()
{
  local -n res="$1"
  echo "start of logic"
  echo "perform logic, to get value"
  res='ok'
}

logic 使用的附加参数的另一个示例：

#!/usr/bin/env bash
logic()
{
  local -n res="$1"
  local a="$2"
  local b="$3"
  echo "start of logic"
  echo "perform logic, to get value"
  if [ $a -gt $b ]; then
    res='ok'
  else
    res='oh no!'
  fi
}

function main ()
{
  result=''
  logic result 3 2

  printf 'result is >%s<\n' "$result"

  if [ "$result" = "ok" ];then
    echo "script successful"
  else
    echo "script failed"
  fi

  logic result 5 10

  printf 'result is >%s<\n' "$result"
}

main "$@"