/*++ /* NAME /* peekfd 3 /* SUMMARY /* determine amount of data ready to read /* SYNOPSIS /* #include <iostuff.h> /* /* ssize_t peekfd(fd) /* int fd; /* DESCRIPTION /* peekfd() attempts to find out how many bytes are available to /* be read from the named file descriptor. The result value is /* the number of available bytes. /* DIAGNOSTICS /* peekfd() returns -1 in case of trouble. The global \fIerrno\fR /* variable reflects the nature of the problem. /* BUGS /* On some systems, non-blocking read() may fail even after a /* positive return from peekfd(). The smtp-sink program works /* around this by using the readable() function instead. /* LICENSE /* .ad /* .fi /* The Secure Mailer license must be distributed with this software. /* AUTHOR(S) /* Wietse Venema /* IBM T.J. Watson Research /* P.O. Box 704 /* Yorktown Heights, NY 10598, USA /*--*/ /* System library. */ #include <sys_defs.h> #include <sys/ioctl.h> #ifdef FIONREAD_IN_SYS_FILIO_H #include <sys/filio.h> #endif #ifdef FIONREAD_IN_TERMIOS_H #include <termios.h> #endif #include <unistd.h> /* Utility library. */ #include "iostuff.h" /* peekfd - return amount of data ready to read */ ssize_t peekfd(int fd) { /* * Anticipate a series of system-dependent code fragments. */ #ifdef FIONREAD int count; return (ioctl(fd, FIONREAD, (char *) &count) < 0 ? -1 : count); #else #error "don't know how to look ahead" #endif }