来自管道的 Bash 输入
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原文地址: http://stackoverflow.com/questions/5710957/
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Bash input from pipe
提问by entropo
I wrote a trivial bash script which dumps a random line from a file or STDIN:
我写了一个简单的 bash 脚本，它从文件或标准输入中随机转储一行：
#!/bin/bash
if [ $# -ne 1 ]
then
echo "Syntax: echo "foo\nbar\nbaz" | randline
FILE (or \'-\' for STDIN)"
echo echo "foo\n\bar\nbaz" | randline -
- display a random line from FILE
exit 1
fi
RAND=`cat /proc/sys/kernel/random/uuid | cut -c1-4 | od -d | head -1 | cut -d' ' -f2`
if [ != "-" ]
then
LINES=`cat "" | wc -l`
LINE=`expr $RAND % $LINES + 1`
head -$LINE | tail -1
else
piped=`cat -`
LINES=`echo "$piped" | wc -l`
LINE=`expr $RAND % $LINES + 1`
echo "$piped" | head -$LINE | tail -1
fi
However, I'd like it to also process STDIN if there are no options passed (but still fail with the help if there's no STDIN from a pipe).
但是，如果没有传递任何选项，我希望它也处理 STDIN（但如果管道中没有 STDIN，则仍然会在帮助下失败）。
That is, I'd like to say:
也就是说，我想说：
#!/bin/bash
if [ "$( tty )" == 'not a tty' ]
then
STDIN_DATA_PRESENT=1
else
STDIN_DATA_PRESENT=0
fi
if [[ $# -ne 1 && $STDIN_DATA_PRESENT -eq 0 ]]
then
echo "Syntax: awk 'BEGIN{srand();}{printf "%04d %s\n", int(rand()*10000), ##代码##}' < $FILENAME | sort | cut -f2- -d' ' | head -1
[FILE (or \'-\' for STDIN)]"
echo ##代码## - display a random line from FILE
echo -e "\nWill also process piped STDIN if no arguments are given."
exit 1
fi
RAND=`cat /proc/sys/kernel/random/uuid | cut -c1-4 | od -d | head -1 | cut -d' ' -f2`
if [[ && != "-" ]]
then
LINES=`cat "" | wc -l`
LINE=`expr $RAND % $LINES + 1`
head -$LINE | tail -1
else
piped=`cat -`
LINES=`echo "$piped" | wc -l`
LINE=`expr $RAND % $LINES + 1`
echo "$piped" | head -$LINE | tail -1
fi
... instead of ...
... 代替 ...
##代码##How can this be done?
如何才能做到这一点？
Edit:
Thanks to Doon!
编辑：
感谢 Doon！
采纳答案by Doon
see here ksh: how to probe stdin?it is for ksh, but an answer for bash is provided
在这里看到ksh：如何探测标准输入？它适用于 ksh，但提供了 bash 的答案
回答by Micha? ?rajer
To get random line from a file you can do:
要从文件中获取随机行，您可以执行以下操作：
##代码##Here we do:
我们这样做：
- add random number to the beginning of each line
- sort output
- remove random number from the beginning of each line
- print first line (of mixed output)
- 在每一行的开头添加随机数
- 排序输出
- 从每一行的开头删除随机数
- 打印第一行（混合输出）
BTW, in if you are using BASH, you can use $RANDOM (provided by bash) variable instead of generating $RAND by your self.
顺便说一句，如果您使用的是 BASH，则可以使用 $RANDOM（由 bash 提供）变量而不是自己生成 $RAND。
