sed — Multine，花括号，搜索替换

Question

If want to replace all:

if (err) {
    callback(err);
    return;
}

With:

if (err) return callback(err);

In my code.

Using sed, I was looking for something like:

sed -n '1h;1!H;${;g;s/if\s*\(err\)\s*{\s*callback\(err\);\s*return;\s*}/if \(err\) return callback\(err\);/g;p;}'

As described here: http://austinmatzko.com/2008/04/26/sed-multi-line-search-and-replace/

But it doesn't seems to work. Any idea?

Answer 1

I agree with other posters that there are better alternatives for sed , but in case you are curious: the fault was in the parentheses. These should not be escaped with a backslash, as this causes them to be handled as grouping symbols, rather than literal parentheses.

This works fine:

sed -n '1h;1!H;${;g;s/if\s*(err)\s*{\s*callback(err);\s*return;\s*}/if (err) return callback(err);/g;p;}'

Answer 2

Through Perl,

$ cat file
foo
if (err) {
    callback(err);
    return;
}
bar
$ perl -0pe 's/(if *(\(err\))) *{\s*(callback)\2;\s*(return);\s*}/$1 $4 $3$2;/g' file
foo
if (err) return callback(err);
bar

Answer 3

使用perl，我能够做到：

perl -i -p0e 's/if \(err\) \{\n\s*callback\(err\)\;\n\s*return;\s*}/if \(err\) return callback\(err\)\;/smg' my_file