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Full Discussion: pipe help
Top Forums Programming pipe help Post 16175 by Perderabo on Tuesday 26th of February 2002 03:07:04 PM
Old 02-26-2002
Nothing that you're saying makes any sense at all.

A process has total control over when a child is created. When it invokes fork(), that is exactly when the process is created. The child exists when the very next statement is executed.

There is no need at all to synchonize the reading and writing on a pipe. The reader do can invoke read() hours before the data is written...it will simply wait unless it sets O_NDELAY in which case it returns immediately...so don't set that option. The reader can also read() hours after the write() on the other end. The data will wait. Neither case can cause a broken pipe, which is the error you complained about. That is caused by the reader exiting prior to the write.

Your real problem is that you'e trying to run a marathon when you can't yet walk.

If you attempt to use pipes in a full-duplex manner or use two pipe to achieve a two-way communication between processes, you will almost certainly cause deadlock. Get the data flowing in a single direction before you try to move on.
 

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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)
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