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| ## page was renamed from BatchFile/Variables | |
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| == Variables == | == Declaration == |
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| Variables are defined with `set` and accessed by surrounding a variable's name with percent signs (`%`). Best practice is to quote variable substitutions. |
Variables are declared with the `set` [[Batch/BuiltinCommands#Set|builtin. |
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| IF "%foo%"=="bar" ECHO Equal }}} === Escaping Special Character === Special characters are escaped using the4 caret (`^`). {{{ set foo=bar ^| baz }}} As with Unix scripting, when commands spawn subshells that re-interpret tokens, it becomes necessary to add an escaped escape character for each layer. {{{ echo foo ^^^& bar | subroutine }}} Double-quoted strings are also interpreted literally. === Escaping Double Quotes === ''Because'' double-quoted strings are interpreted literally, there is further complication for double-quoted strings containing double quotes. There is no universal solution as `cmd.exe` defers interpretation. Consult the specific commands to see if double quotes should be duplicated... {{{ set foo="foo ""bar"" baz" }}} ...or should be escaped in the Unix style... {{{ set foo="foo \"bar\" baz" |
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| == Unset Variables == | == Usage == Variables are accessed by their name. A percent sign (`%`) must surround the name. {{{ set bar=%foo% }}} If a variable's value includes a character that the shell will interpret specially, [[Batch/Quoting|quote]] the variable. {{{ set bar="%foo%" }}} |
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| echo %MyVar% | echo %MyVar% # '%MyVar%' |
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| This prints `%MyVar%`. | ---- |
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| The same behavior will be seen internally, as in conditional statement. | == Special Variables == ||'''Variable'''||'''Value''' || ||`%#` ||number of arguments || ||`%$` ||all arguments as a string || ||`%*` ||all arguments as a string, unmodified by the `shift` [[Batch/BuiltinCommands#Shift|builtin]]|| ||`%@` ||all arguments as a string, but each token is [[Batch/Quoting|quoted]] || === Positional Variables === The name of a command is stored in `%0`. The first argument to the command is stored in `%1`. And so on until the 9th argument, `%9`. For additional arguments, use the `shift` [[Batch/BuiltinCommands#Shift|builtin]] to move them into the 9 accessible variables. To get all arguments as a string (like `%$`) starting from index ''n'', try `%n$`. To get all arguments until index ''n'' (non-inclusive), try `%-n$`. |
Batch File Variables
Declaration
Variables are declared with the set [[Batch/BuiltinCommands#Set|builtin.
set foo=bar
Usage
Variables are accessed by their name. A percent sign (%) must surround the name.
set bar=%foo%
If a variable's value includes a character that the shell will interpret specially, quote the variable.
set bar="%foo%"
If a variable is not set, no substitution occurs.
set MyVar= echo %MyVar% # '%MyVar%'
Special Variables
Variable |
Value |
%# |
number of arguments |
%$ |
all arguments as a string |
%* |
all arguments as a string, unmodified by the shift builtin |
%@ |
all arguments as a string, but each token is quoted |
Positional Variables
The name of a command is stored in %0.
The first argument to the command is stored in %1. And so on until the 9th argument, %9.
For additional arguments, use the shift builtin to move them into the 9 accessible variables.
To get all arguments as a string (like %$) starting from index n, try %n$. To get all arguments until index n (non-inclusive), try %-n$.