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| <h4 class="subsection">17.4.3 Setting Terminal Modes Properly</h4> |
| |
| <p>When you set terminal modes, you should call <code>tcgetattr</code> first to |
| get the current modes of the particular terminal device, modify only |
| those modes that you are really interested in, and store the result with |
| <code>tcsetattr</code>. |
| |
| <p>It's a bad idea to simply initialize a <code>struct termios</code> structure |
| to a chosen set of attributes and pass it directly to <code>tcsetattr</code>. |
| Your program may be run years from now, on systems that support members |
| not documented in this manual. The way to avoid setting these members |
| to unreasonable values is to avoid changing them. |
| |
| <p>What's more, different terminal devices may require different mode |
| settings in order to function properly. So you should avoid blindly |
| copying attributes from one terminal device to another. |
| |
| <p>When a member contains a collection of independent flags, as the |
| <code>c_iflag</code>, <code>c_oflag</code> and <code>c_cflag</code> members do, even |
| setting the entire member is a bad idea, because particular operating |
| systems have their own flags. Instead, you should start with the |
| current value of the member and alter only the flags whose values matter |
| in your program, leaving any other flags unchanged. |
| |
| <p>Here is an example of how to set one flag (<code>ISTRIP</code>) in the |
| <code>struct termios</code> structure while properly preserving all the other |
| data in the structure: |
| |
| <pre class="smallexample"> int |
| set_istrip (int desc, int value) |
| { |
| struct termios settings; |
| int result; |
| |
| result = tcgetattr (desc, &settings); |
| if (result < 0) |
| { |
| perror ("error in tcgetattr"); |
| return 0; |
| } |
| settings.c_iflag &= ~ISTRIP; |
| if (value) |
| settings.c_iflag |= ISTRIP; |
| result = tcsetattr (desc, TCSANOW, &settings); |
| if (result < 0) |
| { |
| perror ("error in tcsetattr"); |
| return 0; |
| } |
| return 1; |
| } |
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