OFMT(3OFMT) Formatted Output Functions OFMT(3OFMT)

ofmt_open, ofmt_print, ofmt_update_winsize, ofmt_strerror, ofmt_close —
data structures and routines for printing output

Formatted output library (libofmt, -lofmt)

#include <ofmt.h>
ofmt_status_t
ofmt_open(const char *fields, const ofmt_field_t *template, uint_t flags, uint_t maxcols, ofmt_handle_t *ofmt);
void
ofmt_print(ofmt_handle_t ofmt, void *cbarg);
void
ofmt_update_winsize(ofmt_handle_t ofmt);
char *
ofmt_strerror(ofmt_handle_t ofmt, ofmt_status_t error, char *buf, uint_t bufsize);
void
ofmt_close(ofmt_handle_t ofmt);

The libofmt library provides data structures and routines for printing output.
Currently this is an internal interface. The interface can and will change without notice as the project needs, at any time.
All output is assumed to be in a columnar format, where each column represents a field to be printed out. Multiple fields in parsable output are separated by ‘:’, with the ‘:’ character itself escaped by a ‘\’ (e.g., IPv6 addresses may be printed as “fe80\:\:1”); single field output is printed as-is. In multiline mode, every [field,value] pair is printed in a line of its own, thus: “field: value”.

The ofmt_field_t data structure used in ofmt_open is defined as follows: 
typedef struct ofmt_field_s { 
	char	*of_name;	/* column name */ 
	uint_t	of_width;	/* output column width */ 
	uint_t	of_id;		/* implementation specific cookie */ 
	ofmt_cb_t *of_cb;	/* callback function defined by caller */ 
} ofmt_field_t;
The ofmt_arg_t data structure which is passed to callback function is defined as follows: 
typedef struct ofmt_arg_s { 
	uint_t	ofmt_id;	/* implementation specific cookie */ 
	uint_t	ofmt_width;	/* output column width */ 
	uint_t	ofmt_index;	/* unused */ 
	void	*ofmt_cbarg;	/* argument passed to ofmt_print() */ 
} ofmt_arg_t;

ofmt_open()

The ofmt_open() function opens a handle returned in ofmt for each set of fields to be printed.
fields is a comma-separated list of the fields that have been selected for output (typically the string passed to -o in the command-line). Columns selected for output are identified by a match between the of_name value in the template and the fields requested. In human-friendly (non machine-parsable) mode, NULL fields, or a value of “all” is treated as a request to print all allowable fields that fit other applicable constraints.
template specifies the list of supported fields, along with formatting information (e.g., field width), and a pointer to a callback function that can provide a string representation of the value to be printed out. The set of supported fields must be a NULL terminated array of type ofmt_field_t, described in Data Structures, as follows: 
{<of_name>, <of_width>, <of_id>, <of_cb> }, 
... 
{<of_name>, <of_width>, <of_id>, <of_cb> }, 
{NULL, 0, 0, NULL}
of_cb is the application-specified callback function with the following prototype that provides a string representation of the value to be printed for the field: 
boolean_t (*of_cb)(ofmt_arg_t *ofmt_arg, char *buf, uint_t bufsize)
The callback must not write beyond bufsize bytes of the string form into buf. If the function successfully translates the field into its string representation and places it into buf, then the callback function should return B_TRUE. Otherwise, the callback function should return B_FALSE.
The interpretation of the of_id field is completely private to the caller, and can be optionally used by the callback function as a cookie to identify the field being printed when a single callback function is shared between multiple template entries.
The flags can be any valid combination of the following:
Machine-parsable mode. Specifying a null or empty fields in the machine-parsable mode will result in a returned error value of OFMT_EPARSENONE. An attempt to create a handle in machine-parsable mode with the fields set to “all” will result in a returned error value of OFMT_EPARSEALL.
Wrap output if field width is exceeded. Currently output is wrapped at whitespace or comma characters.
Multiline mode. Specifying both OFMT_MULTILINE and OFMT_PARSABLE will result in OFMT_EPARSEMULTI.
Right justified output.
The non-zero maxcols limits the number of output columns.

ofmt_print()

The ofmt_print() function prints a row of output.
cbarg points at the arguments to be passed to the callback function for each column in the row. The call to ofmt_print() will result in the callback function of each selected field invoked with of_id, of_width and cbarg embedded in ofmt_arg, described in Data Structures.
The callback function should fill buf with the string to be printed for the field using the data in cbarg.

ofmt_update_winsize()

The ofmt_update_winsize() function updates the window size information (which is initially computed when the handle is created) in the ofmt. If the TIOCGWINSZ ioctl fails, the window size is set to 80x24.

ofmt_strerror()

The ofmt_strerror() function returns error diagnostics in buf using the information in the ofmt and error.
Using a buf size of OFMT_BUFSIZE is recommended.

ofmt_close()

The ofmt_close() function frees any resources allocated for the handle after printing is completed.

If successful, the ofmt_open() function will return OFMT_SUCCESS, with a non-null ofmt_handle. The function returns one of the failure codes (enumerated in ofmt_status_t) listed below otherwise:
out of memory
one or more bad fields with good fields
no valid output fields
"all" is invalid in parsable mode
output fields missing in parsable mode
parsable mode incompatible with wrap mode
no template provided for fields
parsable and multiline don't mix
More information about the type of failure can be obtained by calling ofmt_strerror().
The ofmt_strerror() function returns the buf.

Private.

ioctl(2), strerror(3C), attributes(5)
December 20, 2018 illumos