Plan 9 /sys/man/9/parsecmd

NAME

parsecmd, cmderror, lookupcmd – parse device commands

SYNOPSIS

Cmdbuf* parsecmd(char *a, int n)
void cmderror(Cmdbuf *cb, char *s)
Cmdtab* lookupcmd(Cmdbuf *cb, Cmdtab *ctab, int nctab)

DESCRIPTION

Parsecmd is an interface to tokenize (see getfields(2)), that safely parses a command, with blank–separated fields, as might be written to a device's ctl file. The buffer a and count n can be those passed to the driver's write function. Parsecmd converts the byte array (which might not be null–terminated) to a null– terminated string, trimming any trailing new line, before invoking tokenize to break the string into arguments, interpreting blank and tab as field separators when they are not quoted (in the style of rc(1)). It returns a pointer to a dynamically–allocated Cmdbuf structure, which holds a copy of the string as modified by parsefields, and the resulting fields; it is defined as follows:

typedef struct Cmdbuf { char buf[128]; char *f[16]; int nf; } Cmdbuf;

The array f holds the field pointers; nf gives the number of fields. Cmdbuf is allocated by smalloc (see malloc(9)), and the caller is responsible for freeing it using free. Cmderror prepends the given format with the original command, then calls error(9).
Command strings may be turned into a (typically enumerated) integer with lookupcmd. The catchall * matches any text. Unrecognized commands, or commands given an unacceptable number of arguments generate a call to error. The definition is as follows

struct Cmdtab { int index; char *cmd; int narg; };

The integer index is the number returned on command match. The string cmd is the command name, and narg is 0 (indicating a varadic function) or the number of arguments.


	`/sys/src/9/port/parse.c`