Vi single character change

Shell Programming and Scripting
1

I know this is strictly a programming forum - but I consider vi a programming enabler and the question relates to regex you'd use with awk/sed anyway....

I have a file which is 50,000+ lines long and need to change many many instances of

word_word_word

to be

word+word+word

where 'word' can be any 'word' and it is the underscore character that needs to be changed to a plus character.

I'm happy with

:1,$ s/some pattern/new pattern/g

type changes, but can't seem to nail this.

I've tried

:1,$ s/[Aa-Zz]_[Aa-Zz]/[Aa-Zz]+[Aa-Zz]/g

but that puts many [Aa-Zz] patterns in the file......

Any help humbly appreciated.

-----------------------------------------------------------
Brett

2

Brett, buddy...

%s/\([^_][^_]*\)_\([^_][^_]*\)_\([^_][^_]*\)/\1+\2+\3/g

or similarelly with sed:

sed 's/\([^_][^_]*\)_\([^_][^_]*\)_\([^_][^_]*\)/\1+\2+\3/g' myFile.txt > myNewFile.txt
3

Vgresh,

Can you explain what does the numbers 1 2 3 siginfy here in the script.

Please help me to understand.

4

quoting 'man sed'

                  The characters \n, where  n  is  a
                  digit, will be replaced by the text matched by
                  the  corresponding  backreference  expression.
                  For each backslash (\) encountered in scanning
                  replacement from beginning to end, the follow-
                  ing  character  loses  its special meaning (if
                  any).  It is unspecified what special  meaning
                  is  given  to any character other than &, \ or
                  digits.

let me 'color-code' it:

 %s/\([^_][^_]*\)_\([^_][^_]*\)_\([^_][^_]*\)/\1+\2+\3/g
5

Thanks Vgresh. One more question please.

What does

?

^ signifies starting of the line. But what does _ represent?

I appreciate your reply.

Thanks friend.

6

quoting from 'man regexp':

 1.4      A non-empty string of characters  enclosed  in  square
           brackets  ([])  is a one-character RE that matches any
           one character in that string. If, however,  the  first
           character  of the string is a circumflex (^), the one-
           character RE matches any character except new-line and
           the remaining characters in the string. The ^ has this
           special meaning only if it occurs first in the string.
           The  minus (-) may be used to indicate a range of con-
           secutive characters; for example, [0-9] is  equivalent
           to  [0123456789].  The - loses this special meaning if
           it occurs first (after an initial ^, if any)  or  last
           in  the  string. The right square bracket (]) does not
           terminate such a string when it is the first character
           within  it  (after an initial ^, if any); for example,
           []a-f] matches either a right square  bracket  (])  or
           one  of  the  ASCII letters a through f inclusive.

given the above, the ' [^]' means: any character BUT the ''

7

Thanks Vgresh