Replace a substring in the first column using vi-CodePudding

I have a huge file that has multiple columns as shown below:

J02-31  23.2  ...
J30-09  -45.4  ...
J05 30  56.1  ...
J00-20  -78.2  ...
J11-54 232.0  ...
...      ...  ...

I would like to replace - with $-$ only in the first column, i.e., my output should be like this:

J02$-$31   23.2  ...
J30$-$09  -45.4  ...
J05 30     56.1  ...
J00$-$20  -78.2  ...
J11$-$54  232.0  ...
...      ...     ...

Is there a way to do this using vi. I know that python/pandas can do it, but I am interested in vi usage.

CodePudding user response：

You could do:

:g/^\S*-/s/-/$-$/

Which performs the replacement s/-/$-$/ only on lines which match the pattern /^\S*-/ (ie, those lines which have a - in the first column).

CodePudding user response：

I'd go with

:%s/^\S*\zs-/$-$/

which means:

%s/: apply this substitution for every line
^\S*: read as many non-whitespace characters from the start of the line as possible
\zs: actual match start (you could also capture the \S* above instead and insert it back too)
-: match the - (note: this will only match the last - in the first column, your question isn't really clear if there can be multiple there)
/$-$/: replace the matching part (which is only - thanks to the \zs) with $-$