使用sed(或类似方法)修改变量的内容 [英] Modify the content of variable using sed (or something similar)

问题描述

我写了一个BASH文件，其中包含多个嵌入式循环，形式为

I wrote a BASH file that features multiple embedded loops of the form

for P in {'0.10','0.20', [...] '0.90','1.00'}; do 
   for Q in {'0.10','0.20', [...] ,'0.90','1.00'}; do
    [...] 

我将这些变量用作命令行应用程序的参数，并直接在BASH中创建文件名.我想创建重复项，例如 $ P_REP = 0_10 ，该重复项用下划线替换点，而无需为每种情况或某些硬编码的等效项编写明确的switch语句.我发现解决该问题的(非优雅方法)是

I use these variables both as parameters for a command line application, and to create file names directly in BASH. I would like to create duplicates, say $P_REP=0_10 that replaces the dot by an underscore without writting a explicit switch statement for every case, or some hardcoded equivalent. The (non-elegant way) I found to go about it is to

1. 将 P，Q 的内容转储到临时文件中.
2. 使用 sed的s/./_/-i 在下划线处替换点.
3. 再次读取文件并将其内容加载到新变量中.

1. dump the content of P,Q to a temporary file.
2. replace the dot by an underscore using sed 's/./_/ -i.
3. read the file again and load its content to the new variable.

因此，我想知道是否可以直接在变量的内容上运行sed like命令吗?

Hence, I was wondering if it is possible to run a sed like command directly on the content of a variable?

推荐答案

您可以直接在bash中进行模式替换:

You can do pattern substitution directly in bash:

P_REP=${P/./_}
Q_REP=${Q/./_}

在bash(1)手册页中:

From the bash(1) man page:

参数扩展

$ {parameter/pattern/string}

Paramter Expansion

${parameter/pattern/string}

模式替换.扩展 pattern 来生成模式，就像在路径名扩展中一样.参数被扩展，并且 pattern 与其值的最长匹配被替换为 string .如果 pattern 以/开头，则所有 pattern 匹配项都将替换为 string .通常只替换第一个比赛.如果 pattern 以#开头，则它必须与参数的扩展值的开头匹配.如果 pattern 以％开头，则它必须在参数的扩展值的末尾匹配.如果 string 为null，则删除 pattern 的匹配项，并且/后面的 pattern 可以省略.如果参数是 @ 或 * ，则将替换操作依次应用于每个位置参数，并且扩展名是结果列表.如果parameter是一个用 @ 或 * 下标的数组变量，则将替换操作依次应用于该数组的每个成员，并且扩展为结果列表.

Pattern substitution. The pattern is expanded to produce a pattern just as in pathname expansion. Parameter is expanded and the longest match of pattern against its value is replaced with string. If pattern begins with /, all matches of pattern are replaced with string. Normally only the first match is replaced. If pattern begins with #, it must match at the beginning of the expanded value of parameter. If pattern begins with %, it must match at the end of the expanded value of parameter. If string is null, matches of pattern are deleted and the / following pattern may be omitted. If parameter is @ or *, the substitution operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with @ or *, the substitution operation is applied to each member of the array in turn, and the expansion is the resultant list.

这篇关于使用sed(或类似方法)修改变量的内容的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！