if 1 == 1 (echo yes) else (echo no)
echo Writing a long ^ text here
Why should one know? As said already, it's an interpreter we use, and it's applying some string replacements.
if 1 == 1 ( echo yes ) else ( echo no )
In the first line, variable example is set to 1. In the next "line", containing IF up to the closing bracket, each occurance of %example% is replaced by the value set at that time, which is 1. That's why we almost always use Delayed Expansion. I will not further discuss that feature here; however, it might bring another headache in some (very advanced) cases:
set example=1 if %example% == 1 ( set example=2 echo %example% ) REM result: 1 REM expected: 2
Try it, and try to spot the exclamation mark ...
setlocal EnableDelayedExpansion set pwd=#^!pwd# echo !pwd! %pwd% set pwd=#^^^!pwd# echo !pwd! %pwd%
The pipe character needed escaping, because it is used for piping the output of one command to the input of another. If not escaped, cmd.exe would try to parse it when reading the complete line, which leads to a syntax error because of incomplete FOR.
for /F "tokens=*" %%F in ('dir /a:-d . /s/b ^| find "\temp\"') do del /f %%F
This will output Var as being 2, while without GOTO it results in 1, the value set before the block. This is because cmd.exe will reinterpret the code after it executes a GOTO. This is only a showcase, of course, noone would ever come to the conclusion having to use a goto in a block?!
@echo off set Var=Value 1 if 1==1 ( echo Var when entering the block: %Var%; setting it to "Value 2" now ... set Var=Value 2 goto SomeLabel :SomeLabel echo Var is now: %Var% )
Will not echo anything - because the line is never ended because of the missing ")", and the command is never executed ...
(echo Start for /L %%L in (1,1,100) do echo %%L echo End REM --- Missing closing ")" here
will give you errors that the command " " could not be found.
for %F in (*) do ^ echo %%F
This line will echo both commands. I.e. the line after IF is handled as one command. You could expect, as & is the command separator, that the IF is evaluated up to the ampersand, and after this is starting a new command. Wrong!
if 1 == 1 echo yes & echo another yes
Line 1 will write the last result into output.txt. You could expect that the stdout redirection into a file (> output.txt) would apply to the FOR, but it's not, it is applied to the command (ECHO). And that is meaning that the file is overwritten in each go of the FOR loop. This also means that the file is opened and closed multiple times, which is a performance issue, so even if you use the append (>>) redirector like shown in line 2 it would be bad practice.
for %F in (*) do @echo %F > output.txt for %F in (*) do @echo %F >> output.txt (for %F in (*) do @echo %F) > output.txt
The first and third line actually work, the echoed text is appended to output.txt. After understanding the first line, the second seems to be logically correct - but instead, a syntax error is generated, stating IF is not expected at that position.
>> output.txt echo yes >> output.txt if 1 == 1 echo This is a syntax error >> output.txt (if 1 == 1 echo yes, three) >> output.txt dir c:\* | findstr MyFiles >> output.txt (dir c:\* | findstr MyFiles)
dir c:\* | >> output.txt findstr MyFiles
@echo off call :genscript > script.cmd call script.cmd exit /b :genscript echo @echo off echo dir exit /b
we get the same error as if we would try to use that call on commandline. I did not find any workaround to get this running yet.
call :genscript | findstr dir
Have a question about something in this article? You can receive help directly from the article author. Sign up for a free trial to get started.