如何使bash脚本输出与终端和文件兼容？

在 bash 中，如果我想生成定期状态消息，我可以通过发出热键组合来替换前一个状态消息，例如，如此处、此处或此处所示。当用户直接执行脚本时，这很好，因为它可以让他们随时了解情况，而不会弄乱屏幕。

但是，如果他们想在自动化上下文中使用相同的脚本，则输出将（必须）重定向到文件中：

./test.sh >log.txt

此时，\r、 、\b都\033[0K不起作用。

我如何使其适用于两种模式？

（例如，如果我可以检测输出流是否是文件，那么省略中间消息就足够简单了。）

• 如果可能的话，我想避免在脚本中引入参数。现实世界的版本已经附带了几个。
• 如果可能的话，我想避免处理脚本本身内部的输出流，例如根据这个问题，因此当嵌入到其他脚本中时它不会表现出令人惊讶的行为。

示例代码test.sh：

#!/bin/bash

PREVIOUS_JOB_STATUS=""
SECONDS=0          # auto-incremented by Bash; divide by INTERVAL_SECONDS to get number of retries
INTERVAL_SECONDS=3 # interval between polls to the server
TIMEOUT_SECONDS=10 # how long until we give up, because the server is clearly busy (or dead)
while true; do
  RETRY_SECONDS=$SECONDS
  if [ $RETRY_SECONDS -lt $INTERVAL_SECONDS ]; then # in the real world, here would be      the polling operation
    JOB_STATUS='queued'
  else
    JOB_STATUS='processing'
  fi
  RESULT=1                                          # in the real world, here would be ? of the polling operation
  if [ $RESULT -eq 0 ]; then                            # success
    exit $RESULT
  elif [ $RETRY_SECONDS -gt $TIMEOUT_SECONDS ]; then    # failure (or at least surrender)
    echo "Timeout exceeded waiting for job to finish. Current Job Status is '$JOB_STATUS'. Current result code is '$RESULT'."
    exit $RESULT
  elif [ "$PREVIOUS_JOB_STATUS" = "$JOB_STATUS" ]; then # no change yet,      replace last status message and try again
    echo -en '\033[1A\r\033[K' # move one line up                                : \033[1A ,
                               # move to pos1                                    : \r      ,
                               # delete everything between cursor and end-of-line: \033[K  ,
                               # omit line break                                 : -n
  else                                                  # job status changed, write   new  status message and try again
    PREVIOUS_JOB_STATUS=$JOB_STATUS
  fi
  SLEEP_MESSAGE='Waiting for job to finish. Waited '`printf "%02g" $SECONDS`" s. Current job status is '$JOB_STATUS'. Current result code is '$RESULT'."
  echo $SLEEP_MESSAGE
  sleep $INTERVAL_SECONDS
done

最终输出./test.sh：

Waiting for job to finish. Waited 00 s. Current job status is 'queued'. Current result code is '1'.
Waiting for job to finish. Waited 09 s. Current job status is 'processing'. Current result code is '1'.
Timeout exceeded waiting for job to finish. Current Job Status is 'processing'. Current result code is '1'.

最终输出./test.sh >log.txt 2>&1：

Waiting for job to finish. Waited 00 s. Current job status is 'queued'. Current result code is '1'.
Waiting for job to finish. Waited 03 s. Current job status is 'processing'. Current result code is '1'.
^[[1A^M^[[KWaiting for job to finish. Waited 06 s. Current job status is 'processing'. Current result code is '1'.
^[[1A^M^[[KWaiting for job to finish. Waited 09 s. Current job status is 'processing'. Current result code is '1'.
Timeout exceeded waiting for job to finish. Current Job Status is 'processing'. Current result code is '1'.

期望的最终输出./test.sh >log.txt 2>&1： 等于 的最终输出./test.sh。