AT&T UNIX™PC Unix System V Users Manual - tenox
AT&T UNIX™PC Unix System V Users Manual - tenox AT&T UNIX™PC Unix System V Users Manual - tenox
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VARARGS (5) VARARGS (5) NAME varargs - handle variable argument list SYNOPSIS #include va_alist va_dcl void va_start(pvar) va_list pvar; type va_arg(pvar, type) va_list pvar; void va_end(pvar) va_list pvar; DESCRIPTION This set of macros allows portable procedures that accept variable argument lists to be written. Routines that have variable argument lists [such as printf(3S)] but do not use varargs are inherently nonportable, as different machines use different argument-passing conventions. The va_alist is used as the parameter list in a function header. The va_dcl is a declaration for va_alist . No semicolon should follow va_dcl. The va_list is a type defined for the variable used to traverse the list. The va_start is called to initialize pvar to the beginning of the list. The va_arg will return the next argument in the list pointed to by pvar. Type is the type the argument is expected to be. Different types can be mixed, but it is up to the routine to know what type of argument is expected, as it cannot be determined at runtime. The va_end is used to clean up. Multiple traversals, each bracketed by va_start .. . va_end, are possible. EXAMPLE This example is a possible implementation of ezecl(2). #include #define MAXARGS 100 j* exec! is called by *I I* execl(file, arg1, arg2, ••• , ( char*)O); *I exec!( va_alist) va_dcl { va_list ap; char *file· char *args[MAXARGS] ; - 1-
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