Linux - Bash 将字符串重定向到文件
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/25470652/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Linux - Bash Redirect a String to a file
提问by Alex Brodov
I wrote a simple script that is reading the file content and incrementing a a number inside this file, then i'm holding the change using awk, when i'm trying ro redirect the new String using '>' the whole string is redirected in one line and not like the original was which is 4 lines.
我写了一个简单的脚本，它正在读取文件内容并在这个文件中增加一个数字，然后我使用 awk 保持更改，当我尝试使用 '>' 重定向新字符串时，整个字符串被重定向到一个线而不是像原来的那样是 4 行。
#!/bin/bash -x
# This script is for Incrementing build numbers
path=/home/RND/abrodov
file=tst.txt
tst=`cat $path/$file`
printf "this is the content of the file before incrementing: \n $tst"
newexpr=`awk '/^Build Number/{=+1;}1' /home/RND/abrodov/tst.txt`
printf "\n the new content \n $newexpr"
echo $newexpr > $path/$file
This is the original file before running the script:
这是运行脚本之前的原始文件：
Major Release Number = 4
Minor Release Number = 1
Service Pack Release Number = 2
Build Number = 22
This is the content after i used the script:
这是我使用脚本后的内容：
Major Release Number = 4 Minor Release Number = 1 Service Pack Release Number = 2 Build Number = 23
I'm trying to figure out how can i redirect the text in the original format which is 4 lines.
我想弄清楚如何以原始格式（4 行）重定向文本。
回答by Tom Fenech
You need to wrap your variables in double quotes:
您需要将变量用双引号括起来：
echo "$newexpr" > "$path/$file"
The quotes around $path/$filearen't actually necessary in this case but they do no harm.
$path/$file在这种情况下，周围的引号实际上并不是必需的，但它们没有害处。
More generally, you should also use $( )rather than backticks:
更一般地，您还应该使用$( )而不是反引号：
newexpr=$(awk '/^Build Number/{=+1;}1' "$path/$file")
If you want to achieve the effect of changing the file "in-place", you don't need to use a variable. You can use a temporary file like this:
如果要实现“就地”更改文件的效果，则不需要使用变量。您可以使用这样的临时文件：
awk '/^Build Number/{=+1;}1' "$path/$file" > /tmp/file && mv /tmp/file "$path/$file"
The importance of using quotes
使用引号的重要性
The double quotes preserve the original format of the data. See this simple example, which uses set -xto activate debug mode. The commands that are being executed by the shell are shown on the lines beginning with +. Actually I see that you're already using #!/bin/bash -x. set -xdoes the same thing as that.:
双引号保留数据的原始格式。请参阅此简单示例，它用于set -x激活调试模式。shell 正在执行的命令显示在以+. 实际上，我看到您已经在使用#!/bin/bash -x. set -x做同样的事情。：
$ s="1
> 2"
$ set -x
$ echo $s
+ echo 1 2
1 2
$ echo "$s"
+ echo '1
2'
1
2
The original string contains a newline but when you echoit without quotes, it is interpreted as two arguments to echo, instead of one argument that contains a newline. This is called field splitting. You can learn more about the importance of using double quotes by reading this this wiki article.
原始字符串包含一个换行符，但是当echo它不带引号时，它被解释为 的两个参数echo，而不是一个包含换行符的参数。这称为字段拆分。通过阅读这篇 wiki 文章，您可以了解有关使用双引号的重要性的更多信息。
