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| <title>Debugging with GDB: Input/Output</title> |
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| <a name="Your-Program_0027s-Input-and-Output"></a> |
| <h3 class="section">4.6 Your Program’s Input and Output</h3> |
| |
| <a name="index-redirection"></a> |
| <a name="index-i_002fo"></a> |
| <a name="index-terminal"></a> |
| <p>By default, the program you run under <small>GDB</small> does input and output to |
| the same terminal that <small>GDB</small> uses. <small>GDB</small> switches the terminal |
| to its own terminal modes to interact with you, but it records the terminal |
| modes your program was using and switches back to them when you continue |
| running your program. |
| </p> |
| <dl compact="compact"> |
| <dd><a name="index-info-terminal"></a> |
| </dd> |
| <dt><code>info terminal</code></dt> |
| <dd><p>Displays information recorded by <small>GDB</small> about the terminal modes your |
| program is using. |
| </p></dd> |
| </dl> |
| |
| <p>You can redirect your program’s input and/or output using shell |
| redirection with the <code>run</code> command. For example, |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">run > outfile |
| </pre></div> |
| |
| <p>starts your program, diverting its output to the file <samp>outfile</samp>. |
| </p> |
| <a name="index-tty"></a> |
| <a name="index-controlling-terminal"></a> |
| <p>Another way to specify where your program should do input and output is |
| with the <code>tty</code> command. This command accepts a file name as |
| argument, and causes this file to be the default for future <code>run</code> |
| commands. It also resets the controlling terminal for the child |
| process, for future <code>run</code> commands. For example, |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">tty /dev/ttyb |
| </pre></div> |
| |
| <p>directs that processes started with subsequent <code>run</code> commands |
| default to do input and output on the terminal <samp>/dev/ttyb</samp> and have |
| that as their controlling terminal. |
| </p> |
| <p>An explicit redirection in <code>run</code> overrides the <code>tty</code> command’s |
| effect on the input/output device, but not its effect on the controlling |
| terminal. |
| </p> |
| <p>When you use the <code>tty</code> command or redirect input in the <code>run</code> |
| command, only the input <em>for your program</em> is affected. The input |
| for <small>GDB</small> still comes from your terminal. <code>tty</code> is an alias |
| for <code>set inferior-tty</code>. |
| </p> |
| <a name="index-inferior-tty"></a> |
| <a name="index-set-inferior-controlling-terminal"></a> |
| <p>You can use the <code>show inferior-tty</code> command to tell <small>GDB</small> to |
| display the name of the terminal that will be used for future runs of your |
| program. |
| </p> |
| <dl compact="compact"> |
| <dt><code>set inferior-tty /dev/ttyb</code></dt> |
| <dd><a name="index-set-inferior_002dtty"></a> |
| <p>Set the tty for the program being debugged to /dev/ttyb. |
| </p> |
| </dd> |
| <dt><code>show inferior-tty</code></dt> |
| <dd><a name="index-show-inferior_002dtty"></a> |
| <p>Show the current tty for the program being debugged. |
| </p></dd> |
| </dl> |
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