bash 将文本文件中的行数输出到 Unix 中的屏幕
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Output number of lines in a text file to screen in Unix
提问by Masterminder
Possible Duplicate:
bash echo number of lines of file given in a bash variable
Was wondering how you output the number of lines in a text file to screen and then store it in a variable.
I have a file called stats.txt and when I run wc -l stats.txtit outputs 8 stats.txt
想知道如何将文本文件中的行数输出到屏幕，然后将其存储在变量中。我有一个名为 stats.txt 的文件，当我运行wc -l stats.txt它时会输出8 stats.txt
I tried doing x = wc -l stats.txtthinking it would store the number only and the rest is just for visual but it does not work :(
我试着x = wc -l stats.txt认为它只会存储数字，其余的只是用于视觉，但它不起作用:(
Thanks for the help
谢谢您的帮助
回答by Janito Vaqueiro Ferreira Filho
There are two POSIX standard syntax for doing this:
有两种 POSIX 标准语法可以执行此操作：
x=`cat stats.txt | wc -l`
or
或者
x=$(cat stats.txt | wc -l)
They both run the program and replace the invocation in the script with the standard output of the command, in this case assigning it to the $xvariable. However, be aware that both trim ending newlines (this is actually what you want here, but can be dangerous sometimes, when you expect a newline).
它们都运行程序并用命令的标准输出替换脚本中的调用，在这种情况下将其分配给$x变量。但是，请注意，两者都修剪结束换行符（这实际上是您在这里想要的，但有时可能很危险，当您期望换行符时）。
Also, the second case can be easily nested (example: $(cat $(ls | head -n 1) | wc -l)). You can also do it with the first case, but it is more complex:
此外，第二种情况可以轻松嵌套（例如：）$(cat $(ls | head -n 1) | wc -l)。你也可以用第一种情况来做，但它更复杂：
`cat \`ls | head -n 1\` | wc -l`
There are also quotation issues. You can include these expressions inside double-quotes, but with the back-ticks, you must continue quoting inside the command, while using the parenthesis allows you to "start a new quoting" group:
还有报价问题。您可以将这些表达式包含在双引号内，但使用反引号，您必须在命令内继续引用，而使用括号允许您“开始一个新的引用”组：
"`echo \"My string\"`"
"$(echo "My string")"
Hope this helps =)
希望这会有所帮助 =)
回答by none
you may try:
你可以尝试：
x=`cat stats.txt | wc -l`
or (from the another.anon.coward's comment):
或（来自 another.anon.coward 的评论）：
x=`wc -l < stats.txt`
