135 lines
3.1 KiB
Groff
135 lines
3.1 KiB
Groff
.TH PRINT 3ACK "86/04/02"
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.ad
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.SH NAME
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print, fprint, sprint, doprnt -- very simple formatted-output routines
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.SH SYNOPSIS
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.nf
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.B #include <system.h>
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.B #include <varargs.h>
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.PP
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.B print(format [, arg] ... )
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.B char *format;
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.PP
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.B fprint(filep, format [, arg] ... )
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.B File *filep;
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.B char *format;
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.PP
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.B sprint(s, format [, arg] ... )
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.B char *s, *format;
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.PP
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.B doprnt(filep, format, args)
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.B File *filep;
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.B char *format;
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.B va_list args;
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.fi
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.SH DESCRIPTION
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.I Print
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writes output on standard output.
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.I Fprint
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and
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.I doprnt
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place output on the open file known by
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.IR filep .
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.I Sprint
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places `output' in the string
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.IR s ,
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followed by the character `\\0'.
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.PP
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Each of these functions converts, formats and prints its arguments, following
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the
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.I format
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argument, under control of
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.IR format .
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.I Format
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is a character string which contains two types of objects: plain characters,
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which are simply copied to the output destination, and conversion
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specifications, each of which causes conversion and printing of the next
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successive argument.
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.PP
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A conversion specification is introduced by the character %.
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Following the %, there may be
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.IP \(bu
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an optional row of decimal digits specifying the field width;
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if the converted integral value has fewer characters than
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the field width, it will be blank-padded on the left;
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if the field width begins with a zero, zero-padding will be done;
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.IP \(bu
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the character
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.B l
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specifying that a following
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.BR b ,
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.BR d ,
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.BR o ,
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.B u
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or
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.B x
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corresponds to a long-integer argument;
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.IP \(bu
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a character which indicates the type of conversion to be applied.
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.LP
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.PP
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The conversion characters and their meanings are
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.IP \fBbdox\fP
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The next argument is an integer and is converted to binary, decimal, octal
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or hexadecimal notation respectively.
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.IP \fBc\fP
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Next argument is a character and is put directly into the resulting string.
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the field width is one character.
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.IP \fBs\fP
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Next argument is taken to be a character pointer and characters from the
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string are taken until a null character is reached; a specified field width
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is not taken into account.
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.IP \fBu\fP
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The unsigned integer argument is converted to decimal.
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.LP
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.PP
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Integral arguments are not truncated, even if their size exceeds the specified
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field width.
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Padding takes place only if the specified field width exceeds the actual width.
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.PP
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The printing routines build the string to be printed internally and use
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.I sys_write
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to print it.
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.I Doprnt
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takes
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.I args
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as the address of the arguments of the format string.
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This allows routines, e.g.
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.IR print ,
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to be defined as follows:
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.br
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.RS
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.nf
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#include <varargs.h>
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#include <system.h>
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/*VARARGS*/
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print(va_alist)
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va_dcl
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{
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char *fmt;
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va_list args;
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va_start(args);
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fmt = va_arg(args, char *);
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doprnt(STDOUT, fmt, args);
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va_end(args);
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}
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.fi
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.RE
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.SH FILES
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.nf
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~em/modules/lib/libprint.a
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.fi
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.SH MODULES
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system(3), string(3)
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.SH DIAGNOSTICS
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.PP
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Each illegal conversion specification is replaced by the string "<bad\ format>".
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.SH BUGS
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The maximum length of the string to be printed is 1024 characters.
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.SH SEE ALSO
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printf(3)
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.SH AUTHOR
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Erik Baalbergen <erikb@cs.vu.nl>
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