02-26-2002
i was able to make a father and his son communicate through a pipe but the real problem is: in my example i have no control over when a process is created so i have no control over who is reading and/or writing to a pipe at a certain moment in time.
And i need to have some sort of control of that so i can send data from one process to it's sons and viceversa. How can i achieve that? I believe the most simple method would be using signals to tell the parent when a child is created so that the parent can start writing in the pipe and the child can read from it, but i'm totally lost here.
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LEARN ABOUT ULTRIX
fprintf
printf(3int) printf(3int)
Name
printf, fprintf, sprintf - print formatted output
Syntax
#include <stdio.h>
int printf ( format [, arg ] ... )
char *format;
int fprintf ( stream, format [, arg ] ... )
FILE *stream;
char *format;
int sprintf ( s, format [, arg ] ... )
char *s, *format;
Description
The international functions and are similar to the standard I/O functions. The difference is that the international functions allow you to
use the %digit$ conversion character in place of the % character you use in the standard I/O functions. The digit is a decimal digit n from
1 to 9. The international functions apply conversions to the n th argument in the argument list, rather than to the next unused argument.
You can use the % conversion character in the international functions. However, you cannot mix the % conversion character with the %digit$
conversion character in a single call.
You can indicate a field width or precision by an asterisk (*) instead of a digit string in format strings containing the % conversion
character. If you use an asterisk, you can supply an integer arg that specifies the field width or precision. In format strings containing
the %digit$ conversion character, you can indicate field width or precision by the sequence *digit$. You use a decimal digit from 1 to 9
to indicate which argument contains an integer that specifies the field width or precision.
The conversion characters and their meanings are identical to
You must use each digit argument at least once.
In all cases, the radix character uses is defined by the last successful call to category If category has not been called successfully or
if the radix character is undefined, the radix character defaults to a period (.).
International Environment
LC_NUMERIC If this environment is set and valid, uses the international language database named in the definition to determine radix
character rules.
LANG If this environment variable is set and valid uses the international language database named in the definition to determine
collation and character classification rules. If is defined, its definition supercedes the definition of LANG.
Examples
The following example illustrates using an argument to specify field width:
printf ("%1$d:%2$.*3$d:%4$.*3$d
",
hour, min, precision, sec);
The format string *3$ indicates that the third argument, which is named precision, contains the integer field width specification.
To print the language independent date and time format use the following statement:
printf (format, weekday, month, day, hour, min);
For American use, format could be a pointer to the following string:
"%1$s, %2$s %3$d, %4$d:%5$.2d
"
This string gives the following date format:
Sunday, July 3, 10:02
For use in a German environment, format could be a pointer to the following string:
"%1$s, %3$d. %2$s, %4$d:%5$.2d
"
This string gives the following date format:
Sonntag, 3. Juli, 10:02
Return Values
and return zero for success and EOF for failure. The subroutine returns its first argument for success and EOF for failure.
In the System V and POSIX environments, and return the number of characters transmitted for success. The function ignores the null termi-
nator ( ) when calculating the number of characters transmitted. If an output error occurs, these routines return a negative value.
See Also
intro(3int), setlocale(3), scanf(3int), printf(3s), putc(3s), scanf(3s), stdio(3s)
Guide to Developing International Software
printf(3int)