1CTERMID(3P) POSIX Programmer's Manual CTERMID(3P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 ctermid — generate a pathname for the controlling terminal
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16 #include <stdio.h>
17 char *ctermid(char *s);
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21 The ctermid() function shall generate a string that, when used as a
22 pathname, refers to the current controlling terminal for the current
23 process. If ctermid() returns a pathname, access to the file is not
24 guaranteed.
25 The ctermid() function need not be thread-safe if called with a NULL
27 parameter.
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30 If s is a null pointer, the string shall be generated in an area that
31 may be static, the address of which shall be returned. The application
32 shall not modify the string returned. The returned pointer might be
33 invalidated or the string content might be overwritten by a subsequent
34 call to ctermid(). If s is not a null pointer, s is assumed to point
35 to a character array of at least L_ctermid bytes; the string is placed
36 in this array and the value of s shall be returned. The symbolic con‐
37 stant L_ctermid is defined in <stdio.h>, and shall have a value greater
38 than 0.
39 The ctermid() function shall return an empty string if the pathname
41 that would refer to the controlling terminal cannot be determined, or
42 if the function is unsuccessful.
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45 No errors are defined.
46 The following sections are informative.
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50 Determining the Controlling Terminal for the Current Process
51 The following example returns a pointer to a string that identifies the
52 controlling terminal for the current process. The pathname for the ter‐
53 minal is stored in the array pointed to by the ptr argument, which has
54 a size of L_ctermid bytes, as indicated by the term argument.
55 #include <stdio.h>
57 ...
58 char term[L_ctermid];
59 char *ptr;
60 ptr = ctermid(term);
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64 The difference between ctermid() and ttyname() is that ttyname() must
65 be handed a file descriptor and return a path of the terminal associ‐
66 ated with that file descriptor, while ctermid() returns a string (such
67 as "/dev/tty") that refers to the current controlling terminal if used
68 as a pathname.
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71 L_ctermid must be defined appropriately for a given implementation and
72 must be greater than zero so that array declarations using it are
73 accepted by the compiler. The value includes the terminating null byte.
74 Conforming applications that use multiple threads cannot call ctermid()
76 with NULL as the parameter. If s is not NULL, the ctermid() function
77 generates a string that, when used as a pathname, refers to the current
78 controlling terminal for the current process. If s is NULL, the return
79 value of ctermid() is undefined.
80 There is no additional burden on the programmer—changing to use a hypo‐
82 thetical thread-safe version of ctermid() along with allocating a buf‐
83 fer is more of a burden than merely allocating a buffer. Application
84 code should not assume that the returned string is short, as some
85 implementations have more than two pathname components before reaching
86 a logical device name.
87
89 None.
90
92 ttyname()
93 The Base Definitions volume of POSIX.1‐2008, <stdio.h>
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97 Portions of this text are reprinted and reproduced in electronic form
98 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
99 -- Portable Operating System Interface (POSIX), The Open Group Base
100 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
101 cal and Electronics Engineers, Inc and The Open Group. (This is
102 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
103 event of any discrepancy between this version and the original IEEE and
104 The Open Group Standard, the original IEEE and The Open Group Standard
105 is the referee document. The original Standard can be obtained online
106 at http://www.unix.org/online.html .
107 Any typographical or formatting errors that appear in this page are
109 most likely to have been introduced during the conversion of the source
110 files to man page format. To report such errors, see https://www.ker‐
111 nel.org/doc/man-pages/reporting_bugs.html .
112IEEE/The Open Group 2013 CTERMID(3P)