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如果环境变量未设置，如何记录？

发布于 2024-12-10 16:52:52 字数 45 浏览 0 评论 0原文

如何编写一个 shell 脚本来检查环境变量并在该变量未设置时写入日志文件？

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一口甜 2024-12-17 16:52:52

如果您只想在未设置时显示消息，那么：

if [ -z "${CHOSEN_ENV_VAR}" ]
then echo "CHOSEN_ENV_VAR was not set but should have been" >> log.file
fi

如果您只是希望脚本停止并报告 stderr，那么：（

: ${CHOSEN_ENV_VAR:?'was not set but should have been'}

您可以在交互式 shell 中测试它，但交互式 shell 不会退出。将其放入脚本，然后脚本退出。）

If you only want a message when it is unset, then:

if [ -z "${CHOSEN_ENV_VAR}" ]
then echo "CHOSEN_ENV_VAR was not set but should have been" >> log.file
fi

If you simply want the script to stop and report on stderr, then:

: ${CHOSEN_ENV_VAR:?'was not set but should have been'}

(You can test that in an interactive shell, but the interactive shell won't exit. Put it in a script and the script is exited.)

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七七 2024-12-17 16:52:52

写入日志的命令是logger。
并且您测试是否使用 test -v 设置了变量，因此在您的脚本中必须具有以下行：

if test ! -v VARNAME; then logger Variable VARNAME is unset; fi

编辑：如果您的意思是 log 只是任意日志文件而不是系统日志，您当然可以用 echo bla bla > 替换记录器日志档案。

The command to write to the log is logger.
And you test if a variable is set with test -v, so in your script you must have the lines:

if test ! -v VARNAME; then logger Variable VARNAME is unset; fi

EDIT: In case you mean with log just an arbitrary log file and not the system log, you can of course replace the logger with echo bla bla > log.file.

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凡尘雨 2024-12-17 16:52:52

[ -z "$name" ] 检查 name 是否为空。要测试它是否未设置，请使用 [ -z "${name+isset}" ]。

check() {
  if [ -z "${name+isset}" ]; then
    echo "name is unset"
  elif [ -z "$name" ]; then
    echo "name is empty"
  else
    echo "name is non-empty"
  fi
}
name=me; check name
name=; check name
unset name; check name

[ -z "$name" ] checks whether name is empty. To test whether it is unset, use [ -z "${name+isset}" ].

check() {
  if [ -z "${name+isset}" ]; then
    echo "name is unset"
  elif [ -z "$name" ]; then
    echo "name is empty"
  else
    echo "name is non-empty"
  fi
}
name=me; check name
name=; check name
unset name; check name

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