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| <h4 class="subsection">31.4.3 Examples of <code>sysconf</code></h4> |
| |
| <p>We recommend that you first test for a macro definition for the |
| parameter you are interested in, and call <code>sysconf</code> only if the |
| macro is not defined. For example, here is how to test whether job |
| control is supported: |
| |
| <pre class="smallexample"> int |
| have_job_control (void) |
| { |
| #ifdef _POSIX_JOB_CONTROL |
| return 1; |
| #else |
| int value = sysconf (_SC_JOB_CONTROL); |
| if (value < 0) |
| /* <span class="roman">If the system is that badly wedged,</span> |
| <span class="roman">there's no use trying to go on.</span> */ |
| fatal (strerror (errno)); |
| return value; |
| #endif |
| } |
| </pre> |
| <p>Here is how to get the value of a numeric limit: |
| |
| <pre class="smallexample"> int |
| get_child_max () |
| { |
| #ifdef CHILD_MAX |
| return CHILD_MAX; |
| #else |
| int value = sysconf (_SC_CHILD_MAX); |
| if (value < 0) |
| fatal (strerror (errno)); |
| return value; |
| #endif |
| } |
| </pre> |
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