Windows cmd.exe Variable SubstitutionsThe following substitutions of windows variables eliminate the need for many of the commands that appear in the unix and linux shell environments -- because on windows they are builtin. This is both useful and fast!
Note that you should read and re-read the help provided by the cmd.exe "help" command for the following subjects:
String substitutionsNote that the following string substitutions are built into the cmd.exe command line interpreter. In the following documentation, variable numbers are sometimes used when a variable name will work as well -- not always! Pay attention to the warnings!
Here are the string substitutions documented in various help commands provided in cmd.exe:
In addition, the substituion of variable references has been enhanced in FOR statements and in CALLed functions: You can now use the following optional syntax. In the table below, the letter, I, represents a numbered variable name (like %1 where 1 is the number). These substitutions do not necessarily work on regular variables defined by set. %~I - expands %I removing any surrounding quotes (") %~fI - expands %I to a fully qualified path name %~dI - expands %I to a drive letter only %~pI - expands %I to a path only %~nI - expands %I to a file name only %~xI - expands %I to a file extension only %~sI - expanded path contains short names only %~aI - expands %I to file attributes of file %~tI - expands %I to date/time of file %~zI - expands %I to size of file %~$PATH:1 - searches the directories listed in the PATH environment variable and expands %1 to the fully qualified name of the first one found. If the environment variable name is not defined or the file is not found by the search, then this modifier expands to the empty string. The modifiers can be combined to get compound results: %~dpI - expands %I to a drive letter and path only %~nxI - expands %I to a file name and extension only %~fsI - expands %I to a full path name with short names only %~dp$PATH:1 - searches the directories listed in the PATH environment variable for %1 and expands to the drive letter and path of the first one found (but this would work only in called functions and only for numbered variables) %~ftzaI - expands %I to a DIR like output line From help call: In addition, expansion of batch script argument references (%0, %1, etc.) have been changed as follows: %* in a batch script refers to all the arguments (e.g. %1 %2 %3 %4 %5 ...) From help set: Two new switches have been added to the SET command: SET /A expression SET /P variable=[promptString] The /A switch specifies that the string to the right of the equal sign is a numerical expression that is evaluated. The expression evaluator is pretty simple and supports the following operations, in decreasing order of precedence: () - grouping ! ~ - - unary operators * / % - arithmetic operators + - - arithmetic operators << >> - logical shift & - bitwise and ^ - bitwise exclusive or | - bitwise or = *= /= %= += -= - assignment &= ^= |= <<= >>= If you use any of the logical or modulus operators, you will need to enclose the expression string in quotes. Any non-numeric strings in the expression are treated as environment variable names whose values are converted to numbers before using them. If an environment variable name is specified but is not defined in the current environment, then a value of zero is used. This allows you to do arithmetic with environment variable values without having to type all those % signs to get their values. If SET /A is executed from the command line outside of a command script, then it displays the final value of the expression. The assignment operator requires an environment variable name to the left of the assignment operator. Numeric values are decimal numbers, unless prefixed by 0x for hexadecimal numbers, and 0 for octal numbers. So 0x12 is the same as 18 is the same as 022. Please note that the octal notation can be confusing: 08 and 09 are not valid numbers because 8 and 9 are not valid octal digits. The /P switch allows you to set the value of a variable to a line of input entered by the user. Displays the specified promptString before reading the line of input. The promptString can be empty. Environment variable substitution has been enhanced as follows: %PATH:str1=str2% (set command only) would expand the PATH environment variable, substituting each occurrence of "str1" in the expanded result with "str2". "str2" can be the empty string to effectively delete all occurrences of "str1" from the expanded output. "str1" can begin with an asterisk, in which case it will match everything from the beginning of the expanded output to the first occurrence of the remaining portion of str1. May also specify substrings for an expansion. %PATH:~10,5% (set command only) would expand the PATH environment variable, and then use only the 5 characters that begin at the 11th (offset 10) character of the expanded result. If the length is not specified, then it defaults to the remainder of the variable value. If either number (offset or length) is negative, then the number used is the length of the environment variable value added to the offset or length specified. %PATH:~-10% (set command only) would extract the last 10 characters of the PATH variable. %PATH:~0,-2% (set command only) would extract all but the last 2 characters of the PATH variable. Finally, support for delayed environment variable expansion has been added. This support is always disabled by default, but may be enabled/disabled via the /V command line switch to CMD.EXE. See CMD /? Delayed environment variable expansion is useful for getting around the limitations of the current expansion which happens when a line of text is read, not when it is executed. The following example demonstrates the problem with immediate variable expansion: set VAR=before if "%VAR%" == "before" ( set VAR=after if "%VAR%" == "after" @echo If you see this, it worked ) would never display the message, since the %VAR% in BOTH IF statements is substituted when the first IF statement is read, since it logically includes the body of the IF, which is a compound statement. So the IF inside the compound statement is really comparing "before" with "after" which will never be equal. Similarly, the following example will not work as expected: set LIST= for %i in (*) do set LIST=%LIST% %i echo %LIST% in that it will NOT build up a list of files in the current directory, but instead will just set the LIST variable to the last file found. Again, this is because the %LIST% is expanded just once when the FOR statement is read, and at that time the LIST variable is empty. So the actual FOR loop we are executing is: for %i in (*) do set LIST= %i which just keeps setting LIST to the last file found. Delayed environment variable expansion allows you to use a different character (the exclamation mark) to expand environment variables at but instead will just set the LIST variable to the last file found. Again, this is because the %LIST% is expanded just once when the FOR statement is read, and at that time the LIST variable is empty. So the actual FOR loop we are executing is: for %i in (*) do set LIST= %i which just keeps setting LIST to the last file found. Delayed environment variable expansion allows you to use a different character (the exclamation mark) to expand environment variables at execution time. If delayed variable expansion is enabled, the above examples could be written as follows to work as intended: set VAR=before if "%VAR%" == "before" ( set VAR=after if "!VAR!" == "after" @echo If you see this, it worked ) set LIST= for %i in (*) do set LIST=!LIST! %i echo %LIST% If Command Extensions are enabled, then there are several dynamic environment variables that can be expanded but which don't show up in the list of variables displayed by SET. These variable values are computed dynamically each time the value of the variable is expanded. If the user explicitly defines a variable with one of these names, then that definition will override the dynamic one described below: %CD% - expands to the current directory string. %DATE% - expands to current date using same format as DATE command. %TIME% - expands to current time using same format as TIME command. %RANDOM% - expands to a random decimal number between 0 and 32767. %ERRORLEVEL% - expands to the current ERRORLEVEL value %CMDEXTVERSION% - expands to the current Command Processor Extensions version number. %CMDCMDLINE% - expands to the original command line that invoked the Command Processor.