1CTERMID(P) POSIX Programmer's Manual CTERMID(P)
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6 ctermid - generate a pathname for the controlling terminal
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9 #include <stdio.h>
10 char *ctermid(char *s);
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15 The ctermid() function shall generate a string that, when used as a
16 pathname, refers to the current controlling terminal for the current
17 process. If ctermid() returns a pathname, access to the file is not
18 guaranteed.
19 If the application uses any of the _POSIX_THREAD_SAFE_FUNCTIONS or
21 _POSIX_THREADS functions, it shall ensure that the ctermid() function
22 is called with a non-NULL parameter.
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25 If s is a null pointer, the string shall be generated in an area that
26 may be static (and therefore may be overwritten by each call), the
27 address of which shall be returned. Otherwise, s is assumed to point to
28 a character array of at least L_ctermid bytes; the string is placed in
29 this array and the value of s shall be returned. The symbolic constant
30 L_ctermid is defined in <stdio.h>, and shall have a value greater than
31 0.
32 The ctermid() function shall return an empty string if the pathname
34 that would refer to the controlling terminal cannot be determined, or
35 if the function is unsuccessful.
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38 No errors are defined.
39 The following sections are informative.
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43 Determining the Controlling Terminal for the Current Process
44 The following example returns a pointer to a string that identifies the
45 controlling terminal for the current process. The pathname for the ter‐
46 minal is stored in the array pointed to by the ptr argument, which has
47 a size of L_ctermid bytes, as indicated by the term argument.
48 #include <stdio.h>
51 ...
52 char term[L_ctermid];
53 char *ptr;
54 ptr = ctermid(term);
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59 The difference between ctermid() and ttyname() is that ttyname() must
60 be handed a file descriptor and return a path of the terminal associ‐
61 ated with that file descriptor, while ctermid() returns a string (such
62 as "/dev/tty" ) that refers to the current controlling terminal if used
63 as a pathname.
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66 L_ctermid must be defined appropriately for a given implementation and
67 must be greater than zero so that array declarations using it are
68 accepted by the compiler. The value includes the terminating null byte.
69 Conforming applications that use threads cannot call ctermid() with
71 NULL as the parameter if either _POSIX_THREAD_SAFE_FUNCTIONS or
72 _POSIX_THREADS is defined. If s is not NULL, the ctermid() function
73 generates a string that, when used as a pathname, refers to the current
74 controlling terminal for the current process. If s is NULL, the return
75 value of ctermid() is undefined.
76 There is no additional burden on the programmer-changing to use a hypo‐
78 thetical thread-safe version of ctermid() along with allocating a buf‐
79 fer is more of a burden than merely allocating a buffer. Application
80 code should not assume that the returned string is short, as some
81 implementations have more than two pathname components before reaching
82 a logical device name.
83
85 None.
86
88 ttyname() , the Base Definitions volume of IEEE Std 1003.1-2001,
89 <stdio.h>
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92 Portions of this text are reprinted and reproduced in electronic form
93 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
94 -- Portable Operating System Interface (POSIX), The Open Group Base
95 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
96 Electrical and Electronics Engineers, Inc and The Open Group. In the
97 event of any discrepancy between this version and the original IEEE and
98 The Open Group Standard, the original IEEE and The Open Group Standard
99 is the referee document. The original Standard can be obtained online
100 at http://www.opengroup.org/unix/online.html .
101IEEE/The Open Group 2003 CTERMID(P)