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Bit of a tricky one. How can I correctly escape the following in a batch file?
echo /? display this help text
This particular combination of characters is treated as an "ECHO /?" command:
C:\Batch>ECHO /? display this help text
Displays messages, or turns command-echoing on or off.
ECHO [ON | OFF]
ECHO [message]
Type ECHO without parameters to display the current echo setting.
It does not respond to caret (^) escaping, ie. I've tried ^/? /^? and ^/^?.
NB: As a workaround, I found that inserting other characters in between is enough to bypass the ECHO command line processor, eg:
echo ... /? display this help text
Still, this is not ideal and I wondered if there was a way to acheive the desired output, namely with /? at the start of the echoed message.
791
The backslash (\) character is used to mark these special characters so that they are not interpreted by the shell, but passed on to the command being run (for example, echo ). So to output the string: (Assuming that the value of $X is 5): A quote is ", backslash is \, backtick is `.
In batch files, the percent sign may be "escaped" by using a double percent sign ( %% ). That way, a single percent sign will be used as literal within the command line, instead of being further interpreted.
When echo is turned off, the command prompt doesn't appear in the Command Prompt window. To display the command prompt again, type echo on. To prevent all commands in a batch file (including the echo off command) from displaying on the screen, on the first line of the batch file type: Copy. @echo off.
The ECHO-OFF command suppresses echoing for the terminal attached to a specified process. The ECHO-ON command restores input echoing for a specified process. These commands are frequently used in Procs.
For escaping echo arguments exists many variants, like echo., echo:, echo=
But only echo( seems to be secure against any appended text.
These one fails, if files exists like echo, echo[, echo] or echo+
echo.
echo[
echo]
echo+These one fails, if a file in the current directory exists named my.bat
echo\..\my.bat
echo:\..\my.bat
echo.\..\my.batThese one fails independet of a file
echo/?
echo,/?
echo;/?Only the echo( seems to be always safe against any content
77
For escaping echo arguments, you can use the alternative syntax echo.:
echo./?
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