NXTARG

Section: C Library Functions (3)
Updated: 5/31/86
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NAME

nxtarg - parse arguments from a string

SYNOPSIS

extern char _argbreak;

char *nxtarg (p,brk);
char **p,*brk;

DESCRIPTION

Nxtarg is used to parse a string, picking off one argument with each call of nxtarg. The arguments are separated by some special "break" characters, and may additionally be surrounded by leading and trailing blanks and tabs.

When you have a string which you wish to parse, you should declare a pointer and point to the start of the string:



char string[100];        /* the arg list */
char *pointer;           /* a pointer */
char *argument;          /* one argument */
pointer = string;        /* start of arg list */

Then, each call to nxtarg will fetch the next argument:

: argument = nxtarg (&pointer,"delimiters");

Each call to nxtarg will space the pointer up to one of the delimiters or the end of the string, whichever comes first. Then, the string will be chopped into two pieces: the part containing the argument just parsed, and the rest of the string. The address of the first part will be returned; the pointer will be left pointing to the second part, all ready for the next call to nxtarg. Note that the pointer must not be in a register, since it is passed by address.

The delimiter character (or null character at the end of the string) encountered is placed into the external variable called, _argbreak. You may look at this value to see what delimiter was encountered. If no delimiters were encountered before the end of the string, then the null character will be placed into _argbreak.

If brk, the list of break characters, is 0, then the space character will be used as the only delimiter.

DIAGNOSTICS

If the argument points to the null string, or the end of the string is reached, then a pointer to the null string will be returned. At the end of the string, nxtarg() may be repeated any number of times -- it will continue to leave the pointer unchanged, and return a pointer to the null string.