BASH shell 用变量中的空格扩展参数 [英] BASH shell expand arguments with spaces from variable

问题描述

假设我有一个变量 $ARGS，它包含以下内容:

Say I have a variable $ARGS which contains the following:

file1.txt "second file.txt" file3.txt

如何将 $ARGS 的内容作为参数传递给命令(例如，cat $ARGS)，处理 "second file.txt" 作为一个参数，而不是将其拆分为 "second 和 file.txt"?

How can I pass the contents of $ARGS as arguments to a command (say cat $ARGS, for example), treating "second file.txt" as one argument and not splitting it into "second and file.txt"?

理想情况下，我希望能够将参数完全按照存储在变量中的方式传递给任何命令(从文本文件中读取，但我认为这不相关).

Ideally, I'd like to be able to pass arguments to any command exactly as they are stored in a variable (read from a text file, but I don't think that's pertinent).

谢谢！

推荐答案

可以在没有 bash 数组或 eval 的情况下做到这一点:这是 行为的少数几个地方之一xargs 没有 -0 或 -d 扩展(一种主要产生错误的行为)实际上很有用.

It's possible to do this without either bash arrays or eval: This is one of the few places where the behavior of xargs without either -0 or -d extensions (a behavior which mostly creates bugs) is actually useful.

# this will print each argument on a different line
# ...note that it breaks with arguments containing literal newlines!
xargs printf '%s\n' <<<"$ARGS"

...或...

# this will emit arguments in a NUL-delimited stream
xargs printf '%s\0' <<<"$ARGS"

# in bash 4.4, you can read this into an array like so:
readarray -t -d '' args < <(xargs printf '%s\0' <<<"$ARGS")
yourprog "${args[@]}" # actually run your programs

# in bash 3.x or newer, it's just a bit longer:
args=( );
while IFS= read -r -d '' arg; do
    args+=( "$arg" )
done < <(xargs printf '%s\0' <<<"$ARGS")
yourprog "${args[@]}" # actually run your program

# in POSIX sh, you can't safely handle arguments with literal newlines
# ...but, barring that, can do it like this:
set --
while IFS= read -r arg; do
    set -- "$@" "$arg"
done < <(printf '%s\n' "$ARGS" | xargs printf '%s\n')
yourprog "$@" # actually run your program

...或者，让 xargs 自己执行调用:

...or, letting xargs itself do the invocation:

# this will call yourprog with ARGS given
# ...but -- beware! -- will cause bugs if there are more arguments than will fit on one
# ...command line invocation.
printf '%s\n' "$ARGS" | xargs yourprog

这篇关于BASH shell 用变量中的空格扩展参数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！