如果没有在特定字符串之前将其替换为另一个字符串

问题描述

如何使用Shell脚本在多个文件中将"if"替换为"abc if".但是我不想更改是否在其他时间之前?

How to replace "if" to "abc if" in multiple file using shell scripting. But I don't want to change if when it preceded by else?

例如:

if (var3 == 4'h0)
   a =    bvec[0];
else
if (var3 == 4'h1)
a =    bvec[1];

应转换为

abc if (var3 == 4'h0)
   a =    bvec[0];
else
if (var3 == 4'h1)
a =    bvec[1];

请注意:1. else和if之间可以有不确定的空间或换行.2.文件中还有更多代码3.我希望更改仅在同一文件中进行.4.我想将文件名列表传递给脚本

Please note:1.there are can be indefinite space or a new line between else and if.2. There are more codes present in the file also3. I wanted the changes to occur in the same file only.4. I want to pass a list of filename to the script

我尝试过:

sed -r 's/else[[:blank:]]if/temp1/g;s/if/abc if/g;s/temp1/else if/g' file.v

推荐答案

用于多字符RS，gensub()和单词边界的GNU awk:

WIth GNU awk for multi-char RS, gensub(), and word boundaries:

$ awk -v RS='^$' -v ORS= '{
    gsub(/@/,"@A")
    gsub(/#/,"@B")
    $0 = gensub(/\<else(\s+)if\>/,"#\\1#","g")
    gsub(/\<if\>/,"abc &")
    $0 = gensub(/#(\s+)#/,"else\\1if","g")
    gsub(/@B/,"#")
    gsub(/@A/,"@")
    print
}' file
abc if (var3 == 4'h0)
   a =    bvec[0];
else
if (var3 == 4'h1)
a =    bvec[1];

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