bash 将文件名的前 4 个字符存储到变量中
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Storing the first 4 characters of a filename into a variable
提问by zyxxwyz
This follwing code is part of a script I am writing. Now, for the purposes of this script, I am assuming there is only 1 file in ./src, so this loop should only execute once. Now, in the loop somewhere, I want to take the first 4 characters of $f (the filename) and store it in another variable. I know there is the cut command but I'm not sure if or how that would be used here because I thought cut was used for contents of files, not the files themselves.
以下代码是我正在编写的脚本的一部分。现在，为了这个脚本的目的，我假设 ./src 中只有 1 个文件，所以这个循环应该只执行一次。现在，在某处的循环中，我想取 $f（文件名）的前 4 个字符并将其存储在另一个变量中。我知道有 cut 命令，但我不确定这里是否或如何使用它，因为我认为 cut 用于文件的内容，而不是文件本身。
for f in `ls ./src`
do
echo $f
cd tmp
f="../src/$f"
sh "$f"
done
回答by Michel Feldheim
From http://tldp.org/LDP/abs/html/string-manipulation.html
来自http://tldp.org/LDP/abs/html/string-manipulation.html
Substring Extraction
${string:position}Extracts substring from $string at $position.If the $string parameter is "*" or "@", then this extracts the positional parameters, [1] starting at $position.
${string:position:length}Extracts $length characters of substring from $string at $position.
子串提取
${string:position}从 $position 处的 $string 中提取子字符串。如果 $string 参数是“*”或“@”，那么这将提取位置参数，[1] 从 $position 开始。
${string:position:length}从 $position 处的 $string 中提取子字符串的 $length 个字符。
Example
例子
shortName=${f:0:4}
Have fun!
玩得开心！
回答by anubhava
You can use pure bash way:
您可以使用纯 bash 方式：
${parameter:offset:length}
i.e. to get first chars of $HOMEvariable:
即获取$HOME变量的第一个字符：
echo ${HOME:0:4}
btw your script is also faulty (never parse ls output). It should be like this:
顺便说一句，您的脚本也有问题（永远不要解析 ls 输出）。应该是这样的：
for f in ./src/*
do
echo $f
cd tmp
f="../src/$f"
first4=${f:0:4}
sh "$f"
done
