使用shell命令在模式中替换字符串：sed，awk

Question

Say I have a text file like this:

a;bc;d;{a;b;cd}
ab;cde;f;{ab;c;defg}
ab;{a;b;cd};cde;f
...

and I want to replace all the semicolons in curly brackets by comma. It will look like this after substitution:

a;bc;d;{a,b,cd}
ab;cde;f;{ab,c,defg}
ab;{a,b,cd};cde;f
...

How should I do it in shell command? sed, awk or whatever...

Answer 1

Perl to the rescue:

perl -pe 's/({.*?})/ $1 =~ s=;=,=gr /ge' input

The problem is your expected output is wrong:

a;b;cd         a;b;cd
  |               |
  V               V
a,b,c,d         ab,cd

Answer 2

Through perl which uses positive lookahead ,

$ perl -pe 's/;(?=[^{}]*})/,/g' file
a;bc;d;{a,b,cd}
ab;cde;f;{ab,c,defg}
ab;{a,b,cd};cde;f

Answer 3

sed ':a; s/\(.*\)\({\)\([^;]*\)\(;\)\([^}]*}.*\)/\1\2\3,\5/;t a' file

put a label in the beginning and section off hold patterns and loops around until no more successful substitutions on each line (ta)

E.g.  
a;bc;d;{a;b;cd}morestuff{bsdj;dsfkjl;sdkjl;kd}
ab;cde;f;{ab;c;defg}
ab;{a;b;cd};cde;f

Output: 
a;bc;d;{a,b,cd}morestuff{bsdj,dsfkjl,sdkjl,kd}
ab;cde;f;{ab,c,defg}
ab;{a,b,cd};cde;f