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| -rw-r--r-- | doc/nasmdoc.src | 33 |
1 files changed, 32 insertions, 1 deletions
diff --git a/doc/nasmdoc.src b/doc/nasmdoc.src index a7eb156..fb8a12b 100644 --- a/doc/nasmdoc.src +++ b/doc/nasmdoc.src @@ -3213,10 +3213,17 @@ as shown in the example. \H{otherpreproc} \i{Other Preprocessor Directives} +NASM also has preprocessor directives which allow access to +information from external sources. Currently they include: + The following preprocessor directive is supported to allow NASM to correctly handle output of the cpp C language preprocessor. -\b\c{%line} (see \k{line}) +\b\c{%line} enables NAsM to correctly handle the output of the cpp +C language preprocessor (see \k{line}). + +\b\c{%!} enables NASM to read in the value of an environment variable, +which can then be used in your program (see \k{getenv}). \S{line} \i\c{%line} Directive @@ -3245,6 +3252,30 @@ After reading a \c{%line} preprocessor directive, NASM will report all file name and line numbers relative to the values specified therein. + +\S{getenv} \i\c{%!}\c{<env>}: Read an environment variable. + +The \c{%!<env>} directive makes it possible to read the value of an +environment variable at assembly time. This could, for example, be used +to store the contents of an environment variable into a string, which +could be used at some other point in your code. + +For example, you may want to embed the path to your TEMP directory +in your program. As this is usually stored in an environment variable +called TEMP, this could be coded as follows: + +\c %define TEMP %!TEMP +\c %define quote ' +\c +\c tmpstr db quote TEMP quote + +At the time of writing, this will generate an "unterminated string" +warning at the time of defining "quote", and it will add a space +before and after the string that is read in. I was unable to find +a simple workaround, so I believe that you will need to allow for +the extra spaces if you make use of this feature in that way. + + \C{directive} \i{Assembler Directives} NASM, though it attempts to avoid the bureaucracy of assemblers like |