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shell 脚本的跨平台 getopt

发布于 2024-08-30 09:51:12 字数 77 浏览 12 评论 0原文

我刚刚发现 getopt 不是跨平台的（特别是对于 FreeBSD 和 Linux）。此问题的最佳解决方法是什么？

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辞别 2024-09-06 09:51:12

getopt 命令本质上有两个版本：原始版本和 GNU 增强版本。 GNU 增强版向后兼容原始版本，因此如果您只使用原始版本的功能，那么两者都可以使用。

检测 getopt 的可用版本

您可以检测哪个版本可用，如果 GNU 增强版可用，则使用增强功能；如果 GNU 增强版不可用，则限制自己使用原始功能。增强版有一个-T选项用于测试哪个版本可用。

getopt -T > /dev/null
if [ $? -eq 4 ]; then
    # GNU enhanced getopt is available
    set -- `getopt --long help,output:,version --options ho:v -- "$@"`
else
    # Original getopt is available
    set -- `getopt ho:v "$@"`
fi

考虑使用内置 shell 命令 getopts （带有“s”），因为它更便携。但是，getopts 不支持长选项（例如--help）。

如果您喜欢长选项，请使用getopt并使用上面的测试来查看getopt的GNU增强版本是否可用。如果增强版本不可用，脚本可以正常降级为使用 getopt 的原始版本（不支持长选项名称，也不支持空格）或使用 getopts > （不支持长选项名称）。

正确使用 GNU 增强的 getopt

让 GNU 增强版本正确处理带有空格的参数是很棘手的。其实现方式如下：

ARGS=`getopt --long help,output:,verbose --options ho:v -- "$@"`
if [ $? -ne 0 ]; then
  echo "Usage error (use -h for help)" >&2
  exit 2
fi
eval set -- $ARGS

# Parameters are now sorted: options appear first, followed by --, then arguments
# e.g. entering: "foo bar" -o abc baz -v
#      produces: -o 'abc' -v -- 'foo bar' 'baz'

秘诀是使用 "$@"，其中双引号非常重要（在第 1 行中），并eval 设置命令（第 6 行）。

因此，可以检测和处理 getopt 引发的错误，对 getopt 的调用与 eval 分开进行，两者通过 ARGS 变量链接。

完整的工作示例

PROG=`basename $0`

getopt -T > /dev/null
if [ $? -eq 4 ]; then
  # GNU enhanced getopt is available
  ARGS=`getopt --name "$PROG" --long help,output:,verbose --options ho:v -- "$@"`
else
  # Original getopt is available (no long option names, no whitespace, no sorting)
  ARGS=`getopt ho:v "$@"`
fi
if [ $? -ne 0 ]; then
  echo "$PROG: usage error (use -h for help)" >&2
  exit 2
fi
eval set -- $ARGS

while [ $# -gt 0 ]; do
    case "$1" in
        -h | --help)     HELP=yes;;
        -o | --output)   OUTFILE="$2"; shift;;
        -v | --verbose)  VERBOSE=yes;;
        --)              shift; break;; # end of options
    esac
    shift
done

if [ $# -gt 0 ]; then
  # Remaining parameters can be processed
  for ARG in "$@"; do
    echo "$PROG: argument: $ARG"
  done
fi

echo "$PROG: verbose: $VERBOSE"
echo "$PROG: output: $OUTFILE"
echo "$PROG: help: $HELP"

该示例可以从 https://gist.github.com 下载/hoylen/6607180

维基百科关于 getopts 的条目上的比较表比较了不同的功能。

There are essentially two versions of the getopt command: the original version and the GNU enhanced version. The GNU enhanced version is backward compatible with the original version, so if you only use the features of the original version it will work with both.

Detect which version of getopt is available

You can detect which version is available and use the enhanced features if the GNU enhanced version is available, and limit yourself to the original features if the GNU enhanced version is not available. The enhanced version has a -T option for testing which version is available.

getopt -T > /dev/null
if [ $? -eq 4 ]; then
    # GNU enhanced getopt is available
    set -- `getopt --long help,output:,version --options ho:v -- "$@"`
else
    # Original getopt is available
    set -- `getopt ho:v "$@"`
fi

Consider using built-in shell command getopts (with an "s") instead, because it is more portable. However, getopts does not support long options (e.g. --help).

If you like long options, use getopt and use the above test to see if the GNU enhanced version of getopt is available or not. If the enhanced version is not available, the script can gracefully degrade to either using the original version of getopt (with no support for long option names and no whitespace support) or using getopts (with no support for long option names).

Using GNU enhanced getopt properly

Getting the GNU enhanced version to process arguments with whitespace properly is tricky. Here's how it is done:

ARGS=`getopt --long help,output:,verbose --options ho:v -- "$@"`
if [ $? -ne 0 ]; then
  echo "Usage error (use -h for help)" >&2
  exit 2
fi
eval set -- $ARGS

# Parameters are now sorted: options appear first, followed by --, then arguments
# e.g. entering: "foo bar" -o abc baz -v
#      produces: -o 'abc' -v -- 'foo bar' 'baz'

The secret is to use "$@" where the double quotes are very important (in line 1), and to eval the set command (in line 6).

So errors raised by getopt can be detected and handled, the call to getopt is done separately from the eval with the two linked by the ARGS variable.

Complete working example

PROG=`basename $0`

getopt -T > /dev/null
if [ $? -eq 4 ]; then
  # GNU enhanced getopt is available
  ARGS=`getopt --name "$PROG" --long help,output:,verbose --options ho:v -- "$@"`
else
  # Original getopt is available (no long option names, no whitespace, no sorting)
  ARGS=`getopt ho:v "$@"`
fi
if [ $? -ne 0 ]; then
  echo "$PROG: usage error (use -h for help)" >&2
  exit 2
fi
eval set -- $ARGS

while [ $# -gt 0 ]; do
    case "$1" in
        -h | --help)     HELP=yes;;
        -o | --output)   OUTFILE="$2"; shift;;
        -v | --verbose)  VERBOSE=yes;;
        --)              shift; break;; # end of options
    esac
    shift
done

if [ $# -gt 0 ]; then
  # Remaining parameters can be processed
  for ARG in "$@"; do
    echo "$PROG: argument: $ARG"
  done
fi

echo "$PROG: verbose: $VERBOSE"
echo "$PROG: output: $OUTFILE"
echo "$PROG: help: $HELP"

This example can be downloaded from https://gist.github.com/hoylen/6607180

The comparison table on Wikipedia's entry on getopts compares the different features.

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