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diff --git a/reference/C/MAN/printf.htm b/reference/C/MAN/printf.htm new file mode 100644 index 0000000..cb8bf95 --- /dev/null +++ b/reference/C/MAN/printf.htm @@ -0,0 +1,362 @@ +<TITLE>printf</TITLE> +<body bgcolor="#ffffcc"> +<hr> +<pre> + + + +<h3>PRINTF(3) Linux Programmer's Manual PRINTF(3) +</h3> + +<h3>NAME +</h3> printf, fprintf, sprintf, vprintf, vfprintf, vsprintf - + formatted output conversion + +<h3>SYNOPSIS +</h3> #include <stdio.h> + + int printf( const char *format, ...); + int fprintf( FILE *stream, const char *format, ...); + int sprintf( char *str, const char *format, ...); + + #include <stdarg.h> + + int vprintf( const char *format, va_list ap); + int vfprintf( FILE *stream, const char *format, va_list + ap); + int vsprintf( char *str, char *format, va_list ap); + +<h3>DESCRIPTION +</h3> The printf family of functions produces output according + to a format as described below. Printf and vprintf write + output to stdout, the standard output stream; fprintf and + vfprintf write output to the given output stream; sprintf, + and vsprintf write to the character string str. These + functions write the output under the control of a format + string that specifies how subsequent arguments (or argu- + ments accessed via the variable-length argument facilities + of stdarg(3) are converted for output. These functions + return the number of characters printed (not including the + trailing `\0' used to end output to strings). + + The format string is composed of zero or more directives: + ordinary characters (not %), which are copied unchanged to + the output stream; and conversion specifications, each of + which results in fetching zero or more subsequent argu- + ments. Each conversion specification is introduced by the + character %. The arguments must correspond properly + (after type promotion) with the conversion specifier. + After the %, the following appear in sequence: + + o Zero or more of the following flags: + + # specifying that the value should be con- + verted to an ``alternate form''. For c, d, + i, n, p, s, and u conversions, this option + has no effect. For o conversions, the pre- + cision of the number is increased to force + the first character of the output string to + a zero (except if a zero value is printed + with an explicit precision of zero). For x + and X conversions, a non-zero result has the + string `0x' (or `0X' for X conversions) + prepended to it. For e, E, f, g, and G con- + versions, the result will always contain a + + + +<h3>BSD MANPAGE 29 November 1993 1 +</h3> + + + + +<h3>PRINTF(3) Linux Programmer's Manual PRINTF(3) +</h3> + + decimal point, even if no digits follow it + (normally, a decimal point appears in the + results of those conversions only if a digit + follows). For g and G conversions, trailing + zeros are not removed from the result as + they would otherwise be. + + 0 specifying zero padding. For all conver- + sions except n, the converted value is + padded on the left with zeros rather than + blanks. If a precision is given with a + numeric conversion (d, i, o, u, i, x, and + X), the 0 flag is ignored. + + - (a negative field width flag) indicates the + converted value is to be left adjusted on + the field boundary. Except for n conver- + sions, the converted value is padded on the + right with blanks, rather than on the left + with blanks or zeros. A - overrides a 0 if + both are given. + + (a space) specifying that a blank should be + left before a positive number produced by a + signed conversion (d, e, E, f, g, G, or i). + + + specifying that a sign always be placed + before a number produced by a signed conver- + sion. A + overrides a space if both are + used. + + o An optional decimal digit string specifying a mini- + mum field width. If the converted value has fewer + characters than the field width, it will be padded + with spaces on the left (or right, if the left- + adjustment flag has been given) to fill out the + field width. + + o An optional precision, in the form of a period + (`.') followed by an optional digit string. If + the digit string is omitted, the precision is taken + as zero. This gives the minimum number of digits + to appear for d, i, o, u, x, and X conversions, the + number of digits to appear after the decimal-point + for e, E, and f conversions, the maximum number of + significant digits for g and G conversions, or the + maximum number of characters to be printed from a + string for s conversions. + + o The optional character h, specifying that a follow- + ing d, i, o, u, x, or X conversion corresponds to a + short int or unsigned short int argument, or that a + following n conversion corresponds to a pointer to + a short int argument. + + + +<h3>BSD MANPAGE 29 November 1993 2 +</h3> + + + + +<h3>PRINTF(3) Linux Programmer's Manual PRINTF(3) +</h3> + + o The optional character l (ell) specifying that a + following d, i, o, u, x, or X conversion applies to + a pointer to a long int or unsigned long int argu- + ment, or that a following n conversion corresponds + to a pointer to a long int argument. + + o The character L specifying that a following e, E, + f, g, or G conversion corresponds to a long double + argument. + + o A character that specifies the type of conversion + to be applied. + + A field width or precision, or both, may be indicated by + an asterisk `*' instead of a digit string. In this case, + an int argument supplies the field width or precision. A + negative field width is treated as a left adjustment flag + followed by a positive field width; a negative precision + is treated as though it were missing. + + The conversion specifiers and their meanings are: + + diouxX The int (or appropriate variant) argument is con- + verted to signed decimal (d and i), unsigned octal + (o, unsigned decimal (u, or unsigned hexadecimal (x + and X) notation. The letters abcdef are used for x + conversions; the letters ABCDEF are used for X con- + versions. The precision, if any, gives the minimum + number of digits that must appear; if the converted + value requires fewer digits, it is padded on the + left with zeros. + + DOU The long int argument is converted to signed deci- + mal, unsigned octal, or unsigned decimal, as if the + format had been ld, lo, or lu respectively. These + conversion characters are deprecated, and will + eventually disappear. + + eE The double argument is rounded and converted in the + style [-]d.dddedd where there is one digit before + the decimal-point character and the number of dig- + its after it is equal to the precision; if the pre- + cision is missing, it is taken as 6; if the preci- + sion is zero, no decimal-point character appears. + An E conversion uses the letter E (rather than e) + to introduce the exponent. The exponent always + contains at least two digits; if the value is zero, + the exponent is 00. + + f The double argument is rounded and converted to + decimal notation in the style [-]ddd.ddd, where the + number of digits after the decimal-point character + is equal to the precision specification. If the + precision is missing, it is taken as 6; if the + + + +<h3>BSD MANPAGE 29 November 1993 3 +</h3> + + + + +<h3>PRINTF(3) Linux Programmer's Manual PRINTF(3) +</h3> + + precision is explicitly zero, no decimal-point + character appears. If a decimal point appears, at + least one digit appears before it. + + g The double argument is converted in style f or e + (or E for G conversions). The precision specifies + the number of significant digits. If the precision + is missing, 6 digits are given; if the precision is + zero, it is treated as 1. Style e is used if the + exponent from its conversion is less than -4 or + greater than or equal to the precision. Trailing + zeros are removed from the fractional part of the + result; a decimal point appears only if it is fol- + lowed by at least one digit. + + c The int argument is converted to an unsigned char, + and the resulting character is written. + + s The ``char *'' argument is expected to be a pointer + to an array of character type (pointer to a + string). Characters from the array are written up + to (but not including) a terminating NUL character; + if a precision is specified, no more than the num- + ber specified are written. If a precision is + given, no null character need be present; if the + precision is not specified, or is greater than the + size of the array, the array must contain a termi- + nating NUL character. + + p The ``void *'' pointer argument is printed in hex- + adecimal (as if by %#x or %#lx). + + n The number of characters written so far is stored + into the integer indicated by the ``int *'' (or + variant) pointer argument. No argument is con- + verted. + + % A `%' is written. No argument is converted. The + complete conversion specification is `%%'. + + In no case does a non-existent or small field width cause + truncation of a field; if the result of a conversion is + wider than the field width, the field is expanded to con- + tain the conversion result. + + +<h3>EXAMPLES +</h3> To print a date and time in the form `Sunday, July 3, + 10:02', where weekday and month are pointers to strings: + #include <stdio.h> + fprintf(stdout, "%s, %s %d, %.2d:%.2d\n", + weekday, month, day, hour, min); + + To print to five decimal places: + + + +<h3>BSD MANPAGE 29 November 1993 4 +</h3> + + + + +<h3>PRINTF(3) Linux Programmer's Manual PRINTF(3) +</h3> + + #include <math.h> + #include <stdio.h> + fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0)); + + To allocate a 128 byte string and print into it: + #include <stdio.h> + #include <stdlib.h> + #include <stdarg.h> + char *newfmt(const char *fmt, ...) + { + char *p; + va_list ap; + if ((p = malloc(128)) == NULL) + return (NULL); + va_start(ap, fmt); + (void) vsnprintf(p, 128, fmt, ap); + va_end(ap); + return (p); + } + +</pre> +<hr> +<h3>SEE ALSO +</h3><p> +<a href=printf.htm>printf</a>, +<a href=scanf.htm>scanf</a>, +<pre> + +<h3>STANDARDS +</h3> The fprintf, printf, sprintf, vprintf, vfprintf, and + vsprintf functions conform to ANSI C3.159-1989 (``ANSI + C''). + +<h3>BUGS +</h3> Some floating point conversions under Linux cause memory + leaks. + + The conversion formats %D, %O, and %U are not standard and + are provided only for backward compatibility. These may + not be provided under Linux. + + The effect of padding the %p format with zeros (either by + the 0 flag or by specifying a precision), and the benign + effect (i.e., none) of the # flag on %n and %p conver- + sions, as well as other nonsensical combinations such as + %Ld, are not standard; such combinations should be + avoided. + + Because sprintf and vsprintf assume an infinitely long + string, callers must be careful not to overflow the actual + space; this is often impossible to assure. + + + + + + + + + + + +<h3>BSD MANPAGE 29 November 1993 5 +</h3> + +
</pre> +<P> +<hr> +<p> +<center> +<table border=2 width=80%> +<tr align=center> +<td width=25%> +<a href=../cref.html>Top</a> +</td><td width=25%> +<a href=../master_index.html>Master Index</a> +</td><td width=25%> +<a href=../SYNTAX/keywords.html>Keywords</a> +</td><td width=25%> +<a href=../FUNCTIONS/funcref.htm>Functions</a> +</td> +</tr> +</table> +</center> +<p> +<hr> + +This manual page was brought to you by <i>mjl_man V-2.0</i> |