Xinu7/man/man3/printf.doc
PRINTF(3) Xinu Programmer's Manual PRINTF(3)
NAME
printf, fprintf, sprintf - formatted output conversion
SYNOPSIS
printf(format [, arg ] ... )
char *format;
fprintf(dev, format [, arg ] ... )
int dev;
char *format;
sprintf(s, format [, arg ] ... )
char *s, format;
DESCRIPTION
_P_r_i_n_t_f writes formatted output on device _C_O_N_S_O_L_E. _F_p_r_i_n_t_f
writes formatted output on the named output _d_e_v_i_c_e. _S_p_r_i_n_t_f
places formatted `output' in the string _s, followed by the
character `\0'.
Each of these functions converts, formats, and prints its
arguments after the format under control of the format argu-
ment. The format argument is a character string which con-
tains two types of objects: plain characters, which are sim-
ply copied to the output stream, and conversion specifica-
tions, each of which causes conversion and printing of the
next successive _a_r_g.
Each conversion specification is introduced by the character
%. Following the %, there may be, in the following order,
- an optional minus sign `-' which specifies _l_e_f_t _a_d_j_u_s_t_-
_m_e_n_t of the converted value in the indicated field;
- an optional digit string specifying a _f_i_e_l_d _w_i_d_t_h; if
the converted value has fewer characters than the field
width it will be blank-padded on the left (or right, if
the left-adjustment indicator has been given) to make
up the field width; if the field width begins with a
zero, zero-padding will be done instead of blank-
padding;
- an optional period `.' which serves to separate the
field width from the next digit string;
- an optional digit string specifying a _p_r_e_c_i_s_i_o_n which
specifies the maximum number of characters to be
printed from a string;
- the character l specifying that a following d, o, x, or
u corresponds to a long integer _a_r_g. (A capitalized
conversion code accomplishes the same thing.)
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PRINTF(3) Xinu Programmer's Manual PRINTF(3)
- a character which indicates the type of conversion to
be applied.
A field width or precision may be `*' instead of a digit
string. In this case an integer _a_r_g supplies the field
width or precision.
The conversion characters and their meanings are
dox The integer _a_r_g is converted to decimal, octal, or hex-
adecimal notation respectively.
c The character _a_r_g is printed. Null characters are
ignored.
s _A_r_g is taken to be a string (character pointer) and
characters from the string are printed until a null
character or until the number of characters indicated
by the precision specification is reached; however if
the precision is 0 or missing all characters up to a
null are printed.
u The unsigned integer _a_r_g is converted to decimal and
printed (the result will be in the range 0 through
65535 on the LSI-11 for normal integers and 0 through
4294967295 for long integers).
% Print a `%'; no argument is converted.
In no case does a non-existent or small field width cause
truncation of a field; padding takes place only if the
specified field width exceeds the actual width. Characters
generated by _p_r_i_n_t_f are printed by PUTC(2).
Examples
To print a date and time in the form `Sunday, July 3,
10:02', where _w_e_e_k_d_a_y and _m_o_n_t_h are pointers to null-
terminated strings:
printf("%s, %s %d, %02d:%02d", weekday, month, day,
hour, min);
SEE ALSO
putc(2), scanf(3)
BUGS
Very wide fields (>128 characters) fail.
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