下面是我写的一个脚本来说明这个问题：

#!/bin/bash

cat_then_tac()
{
    echo cat
    cat "$1"
    echo tac
    tac "$1"
    echo end
}

seq 3 > file1

echo
echo using proper file: works as expected
cat_then_tac file1

echo
echo using process substitution: stream is somehow consumed upon first use and tac has nothing to work on
cat_then_tac <(seq 3)

rm file1

这是它的输出：

using proper file: works as expected
cat
1
2
3
tac
3
2
1
end

using process substitution: stream is somehow consumed upon first use and tac has nothing to work on
cat
1
2
3
tac
end

显然，可以通过首先保存流（在文件或变量中）并根据需要多次使用它来解决这个问题。但为什么会发生这种消费呢？
后来，我在Unix-StackExchange上发现这个问题与同一件事有关。它还包含值得一看的信息：Bash Reuse Process Substitution File