Removing non alphanumeric characters in a batch variable - batch-file

Question

In batch, how would I remove all non alphanumeric (a-z,A-Z,0-9,_) characters from a variable?
I'm pretty sure I need to use findstr and a regex.

Answer 1

The solutionof MC ND works, but it's really slow (Needs ~1second for the small test sample).
This is caused by the echo "!_buf!"|findstr ... construct, as for each character the pipe creates two instances of cmd.exe and starts findstr.
But this can be solved also with pure batch.
Each character is tested if it is in the map variable
:test
set "_input=Th""i\s&& is not good _maybe_???"
set "_output="
set "map=abcdefghijklmnopqrstuvwxyz 1234567890"
:loop
if not defined _input goto endLoop
for /F "delims=*~ eol=*" %%C in ("!_input:~0,1!") do (
if "!map:%%C=!" NEQ "!map!" set "_output=!_output!%%C"
)
set "_input=!_input:~1!"
goto loop
:endLoop
echo(!_output!
And it could be speed up when the goto loop is removed.
Then you need to calculate the stringLength first and iterate then with a FOR/L loop over each character.
This solution is ~6 times faster than the above method and ~40 times faster than the solution of MC ND
set "_input=Th""i\s&& is not good _maybe_!~*???"
set "_output="
set "map=abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ 1234567890"
%$strLen% len _input
for /L %%n in (0 1 %len%) DO (
for /F "delims=*~ eol=*" %%C in ("!_input:~%%n,1!") do (
if "!map:%%C=!" NEQ "!map!" set "_output=!_output!%%C"
)
)
exit /b
The macro $strlen can be defined with
set LF=^
::Above 2 blank lines are required - do not remove
#set ^"\n=^^^%LF%%LF%^%LF%%LF%^^":::: StrLen pResult pString
set $strLen=for /L %%n in (1 1 2) do if %%n==2 (%\n%
for /F "tokens=1,2 delims=, " %%1 in ("!argv!") do (%\n%
set "str=A!%%~2!"%\n%
set "len=0"%\n%
for /l %%A in (12,-1,0) do (%\n%
set /a "len|=1<<%%A"%\n%
for %%B in (!len!) do if "!str:~%%B,1!"=="" set /a "len&=~1<<%%A"%\n%
)%\n%
for %%v in (!len!) do endlocal^&if "%%~b" neq "" (set "%%~1=%%v") else echo %%v%\n%
) %\n%
) ELSE setlocal enableDelayedExpansion ^& set argv=,

Answer 2

EDITED - #jeb is right. This works but is really, really slow.
#echo off
setlocal enableextensions enabledelayedexpansion
set "_input=Th""i\s&& is not good _maybe_???"
set "_output="
:loop
if not defined _input goto endLoop
set "_buf=!_input:~0,1!"
set "_input=!_input:~1!"
echo "!_buf!"|findstr /i /r /c:"[a-z 0-9_]" > nul && set "_output=!_output!!_buf!"
goto loop
:endLoop
echo !_output!
endlocal
So, back to the drawing board. How to make it faster? lets try to do as less operations as we can and use as much long substring as we can. So, do it in two steps
1.- Remove all bad characters that can generate problems. To do it we will use the hability of for command to identify these chars as delimiters , and then join the rest of the sections of god characters of string
2.- Remove the rest of the bad characters, locating them in string using the valids charactes as delimiters to find substrings of bad characters, replacing then in string
So, we end with (sintax adapted to what has been answered here)
#echo off
setlocal enableextensions enabledelayedexpansion
rem Test empty string
call :doClean "" output
echo "%output%"
rem Test mixed strings
call :doClean "~~asd123#()%%%^"^!^"~~~^"""":^!!!!=asd^>^<bm_1" output
echo %output%
call :doClean "Thi\s&& is ;;;;not ^^good _maybe_!~*???" output
echo %output%
rem Test clean string
call :doClean "This is already clean" output
echo %output%
rem Test all bad string
call :doClean "*******//////\\\\\\\()()()()" output
echo "%output%"
rem Test long string
set "zz=Thi\s&& is not ^^good _maybe_!~*??? "
set "zz=TEST: %zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%%zz%"
call :doClean "%zz% TEST" output
echo %output%
rem Time long string
echo %time%
for /l %%# in (1 1 100) do call :doClean "%zz%" output
echo %time%
exit /b
rem ---------------------------------------------------------------------------
:doClean input output
setlocal enableextensions enabledelayedexpansion
set "map=abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890 "
set "input=%~1"
set "output="
rem Step 1 - Remove critical delimiters
(
:purgeCritical
for /L %%z in (1 1 10) do (
for /f tokens^=1^-9^,^*^ delims^=^=^"^"^~^;^,^&^*^%%^:^!^(^)^<^>^^ %%a in ("!input!") do (
set "output=!output!%%a%%b%%c%%d%%e%%f%%g%%h%%i"
set "input=%%j"
)
if not defined input goto outPurgeCritical
)
goto purgeCritical
)
:outPurgeCritical
rem Step 2 - remove any remaining special character
(
:purgeNormal
for /L %%z in (1 1 10) do (
set "pending="
for /f "tokens=1,* delims=%map%" %%a in ("!output!") do (
set "output=!output:%%a=!"
set "pending=%%b"
)
if not defined pending goto outPurgeNormal
)
goto purgeNormal
)
:outPurgeNormal
endlocal & set "%~2=%output%"
goto :EOF
Maybe not the fastest, but at least a "decent" solution

Answer 3

#echo eof
call :purge "~~asd123#()%%%^"^!^"~~~^:^=asd^>^<bm_1" var
echo (%var%)
goto :eof
:purge StrVar [RtnVar]
setlocal disableDelayedExpansion
set "str1=%~1"
setlocal enableDelayedExpansion
for %%a in ( - ! # # $ % ^^ ^& + \ / ^< ^> . ' [ ] { } ` ^| ^" ) do (
set "str1=!str1:%%a=!"
)
rem dealing with some delimiters
set "str1=!str1:(=!"
set "str1=!str1:)=!"
set "str1=!str1:;=!"
set "str1=!str1:,=!"
set "str1=!str1:^^=!"
set "str1=!str1:^~=!"
set "temp_str="
for %%e in (%str1%) do (
set "temp_str=!temp_str!%%e"
)
endlocal & set "str1=%temp_str%"
setlocal disableDelayedExpansion
set "str1=%str1:!=%"
set "str1=%str1::=%"
set "str1=%str1:^^~=%"
for /f "tokens=* delims=~" %%w in ("%str1%") do set "str1=%%w"
endlocal & set "str1=%str1%"
endlocal & if "%~2" neq "" (set %~2=%str1%) else echo %str1%
goto :eof
Still cannot deal with ~ and = but working on it
EDIT: = now will be cleared
EDIT: ~ now will be cleared