Batch: Replacing just the first character in a string if it is a certain character

Question

I have several datalines like so:

v1.4.00.29                                                           
- SP.CNG v1.0.2.2                                                           
Update Kit - Secure USB Token v1.1.1.1                                                           
- HI_3997 v1.0.3997.1                                                           
- HI_4009 v1.0.4009.1                                                           
- HI_3585 v1.0.3585                                                           
Update Kit - RM4 v1.0.1202.4                                                           
Update Kit - DN Series v1.0.4.1

Is there some easy way to check if the first character is a - and then delete this PLUS the space next to them so that the line is aligned to the other lines.

My first try was just to delete the -and spacesresulting in a not looking result as ALL - are replaced:

set tmp=!tmp:-=!
set tmp=!tmp: =!

why not simply remove "dash+space" (`set tmp=!tmp:- =!`) instead of removing every dash and every space? — Stephan, Dec 18 '19 at 11:23
He then also removes i there is a DASh and SPACE at different positions — SRel, Dec 18 '19 at 11:25
...which may or may not be a good idea. If not, TripeHound's solution is the best to remove them only at the beginning. (I just wondered why you removed both chars independently instead of their combination) — Stephan, Dec 18 '19 at 11:30
To align with other lines, I would suggest it may be better to prepend eleven spaces to any lines beginning with `-`! — Compo, Dec 18 '19 at 11:36

score 3 · Accepted Answer · answered Dec 18 '19 at 11:09

You can do this using the "substring" method of referring to environment variables. In brief:

%TMP:~n,m%

will extract m characters from TMP, starting with the n^th, where counting starts from zero. (You can also omit ,m to get "the rest of the string" and use negative numbers to mean "from the end of the string" – see the output of SET /? for more details).

In your case, something like the following should work:

if "%TMP:~0,2%" == "- "     set "TMP=%TMP:~2%"

This checks whether the first two characters are a minus and a space (you could relax this to just checking the first character if needed). If there's a match, it replaces TMP with all characters starting with the third (0=1^st, 1=2^nd etc.).

@SRel While they can sometimes be fiddly, the substring commands can be quite powerful. For instance, with `SET Y=4` and `SET STR=abcdefgh`, then `echo !STR:~%Y%,1!` will extract the 5th letter (`e`). (Providing `setlocal enabledelayedexpansion` is in effect). — TripeHound, Dec 18 '19 at 11:30

aschipfl · Answer 2 · 2020-03-17T09:18:10.463

You might want to try the following code that uses sub-string substitution (the string to process is stored in variale tmp):

if "- !tmp:*- !"=="!tmp!" set "tmp=!tmp:*- =!"

This removes everything up to and including the first occurrence of - + SPACE from the string and precedes the result with - + SPACE; if this is now equal to the original string then the first - + SPACE must be at the beginning, so remove it; otherwise do not alter the string.

Batch: Replacing just the first character in a string if it is a certain character

2 Answers2