tcsetattr(3c)

1tcsetattr(3C)            Standard C Library Functions            tcsetattr(3C)
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NAME

6       tcsetattr - set the parameters associated with the terminal
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SYNOPSIS

9       #include <termios.h>
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11       int tcsetattr(int fildes, int optional_actions,
12            const struct termios *termios_p);
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DESCRIPTION

16       The tcsetattr() function sets the parameters associated with the termi‐
17       nal referred to by the  open  file  descriptor  fildes  (an  open  file
18       descriptor  associated with a terminal) from the termios structure (see
19       termio(7I)) referenced by termios_p as follows:
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21           o      If optional_actions is TCSANOW, the change will occur  imme‐
22                  diately.
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24           o      If  optional_actions  is  TCSADRAIN,  the  change will occur
25                  after all output written  to  fildes  is  transmitted.  This
26                  function should be used when changing parameters that affect
27                  output.
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29           o      If optional_actions is  TCSAFLUSH,  the  change  will  occur
30                  after  all  output written to fildes is transmitted, and all
31                  input so far received but not read will be discarded  before
32                  the change is made.
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35       If  the  output baud rate stored in the termios structure pointed to by
36       termios_p is the zero baud rate, B0, the modem control  lines  will  no
37       longer be asserted. Normally, this will disconnect the line.
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40       If  the  input  baud rate stored in the termios structure pointed to by
41       termios_p is 0, the input baud rate given to the hardware will  be  the
42       same as the output baud rate stored in the termios structure.
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45       The  tcsetattr()  function  will  return successfully if it was able to
46       perform any of the requested actions, even if  some  of  the  requested
47       actions  could  not  be  performed. It will set all the attributes that
48       implementation supports as requested and leave all the  attributes  not
49       supported  by  the  implementation unchanged. If no part of the request
50       can be honoured, it will return −1 and set  errno  to  EINVAL.  If  the
51       input  and  output  baud rates differ and are a combination that is not
52       supported, neither baud rate is changed. A  subsequent  call  to  tcge‐
53       tattr(3C) will return the actual state of the terminal device (reflect‐
54       ing both the changes made and not  made  in  the  previous  tcsetattr()
55       call).  The  tcsetattr()  function  will  not  change the values in the
56       termios structure whether or not it actually accepts them.
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59       The effect of tcsetattr() is undefined if  the  value  of  the  termios
60       structure  pointed to by termios_p was not derived from the result of a
61       call to tcgetattr(3C) on fildes;  an  application  should  modify  only
62       fields  and  flags  defined  by this document between the call to tcge‐
63       tattr(3C) and tcsetattr(), leaving all other fields and  flags  unmodi‐
64       fied.
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67       No  actions  defined by this document, other than a call to tcsetattr()
68       or a close of the last file descriptor in the  system  associated  with
69       this terminal device, will cause any of the terminal attributes defined
70       by this document to change.
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73       Attempts to use tcsetattr() from a process which is a member of a back‐
74       ground process group on a fildes associated with its controlling termi‐
75       nal, will cause the process group to be sent a SIGTTOU signal.  If  the
76       calling process is blocking or ignoring SIGTTOU signals, the process is
77       allowed to perform the operation, and no signal is sent.
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USAGE

80       If trying to change baud rates, applications  should  call  tcsetattr()
81       then  call  tcgetattr(3C)  in  order  to determine what baud rates were
82       actually selected.
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RETURN VALUES

85       Upon successful completion, 0 is returned. Otherwise,  −1  is  returned
86       and errno is set to indicate the error.
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ERRORS

89       The tcsetattr() function will fail if:
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91       EBADF     The fildes argument is not a valid file descriptor.
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94       EINTR     A signal interrupted tcsettattr().
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97       EINVAL    The optional_actions argument is not a supported value, or an
98                 attempt was made to change an attribute  represented  in  the
99                 termios structure to an unsupported value.
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102       ENOTTY    The file associated with fildes is not a terminal.
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106       The tcsetattr() function may fail if:
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108       EIO    The  process  group  of the writing process is orphaned, and the
109              writing process is not ignoring or blocking SIGTTOU.
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ATTRIBUTES

113       See attributes(5) for descriptions of the following attributes:
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118       ┌─────────────────────────────┬───────────────────────────────┐
119       │      ATTRIBUTE TYPE         │       ATTRIBUTE VALUE         │
120       ├─────────────────────────────┼───────────────────────────────┤
121       │Interface Stability          │Standard                       │
122       ├─────────────────────────────┼───────────────────────────────┤
123       │MT-Level                     │MT-Safe, and Async-Signal-Safe │
124       └─────────────────────────────┴───────────────────────────────┘
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