ptsname(3C)

NAME

ptsname, ptsname_r — get the pathname of a slave pty (pseudo-terminal)

SYNOPSIS

#include <stdlib.h>

char * ptsname (int fildes);

char * ptsname_r (int fildes, char *slavename, int len);

Remarks:

ptsname() and ptsname_r() support STREAMS pty (see ptm(7) and pts(7)), and non-STREAMS pty (see pty(7)) which have different device naming conventions. Notice that the STREAMS pty, being an optional feature, is supported only when it is installed on the system.

ptsname() and ptsname_r() are useful only on systems that follow the insf(1M) naming conventions for pty (STREAMS and non-STREAMS).

DESCRIPTION

The passed parameter, fildes, is a file descriptor of an opened master pty. ptsname() generates the name of the slave pty corresponding to this master pty. This means that their minor numbers will be identical.

ptsname_r() is the reentrant version of the ptsname() function. The passed parameter, slavename, is a pointer to a character array for the resulting null-terminated pathname of the slave pty. The passed parameter, len, indicates the length of this character array which must be at least 32 bytes long.

RETURN VALUE

Upon successful completion, ptsname() returns a string containing the full path name of a slave pty. Otherwise, a NULL pointer is returned. The return value is pointed to static data area which is overwritten with each call to ptsname(), so it should be copied if it is to be saved.

Upon successful completion, ptsname_r() stores the resulting slave name in the character array pointed to by the slavename parameter, and returns a value of 0 (zero). Otherwise, it returns a value of -1.

ERRORS

ptsname() fails and returns a NULL pointer under the following conditions:

File descriptor does not refer to an open master pty.
Request falls outside pty name-space.
Pty device naming conventions have not been followed.
ptsname() failed to find a match.

ptsname_r() also fails under the above-mentioned conditions but instead it returns a -1 and sets errno to ENXIO. ptsname_r() returns a -1 and sets errno to ERANGE if the slavename parameter is invalid or the len parameter is too small,

EXAMPLES

The following example shows how ptsname() is typically used for non-STREAMS pty to obtain the pathname of the slave pty corresponding to a master pty obtained through a pty clone open.

int fd_master; 
char *path; 
     ...

     fd_master = open("/dev/ptym/clone", O_RDONLY); 
     path = ptsname(fd_master); 

The following example shows how ptsname() is typically used on obtaining the pathname of the STREAMS slave pty corresponding to a STREAMS master pty.

int fd_master, fd_slave; 
char *slave; 
     ...

     fd_master = open("/dev/ptmx", O_RDWR); 
     grantpt(fd_master); 
     unlockpt(fd_master); 
     slave = ptsname(fd_master); 
     fd_slave = open(slave, O_RDWR); 
     ioctl(fd_slave, I_PUSH, "ptem"); 
     ioctl(fd_slave, I_PUSH, "ldterm"); 

AUTHOR

ptsname() and ptsname_r() were developed by HP and OSF.

ptsname(3C)

Technical documentation

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