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| <tr><td width=20><td><b>ERRSTR(3)</b><td align=right><b>ERRSTR(3)</b> |
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| <p><font size=+1><b>NAME </b></font><br> |
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| errstr, rerrstr, werrstr – description of last system call error<br> |
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| <p><font size=+1><b>SYNOPSIS </b></font><br> |
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| <tt><font size=+1>#include <u.h><br> |
| #include <libc.h> |
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| <tt><font size=+1>int errstr(char *err, uint nerr) |
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| <tt><font size=+1>void rerrstr(char *err, uint nerr) |
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| <tt><font size=+1>void werrstr(char *fmt, ...)<br> |
| </font></tt> |
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| <p><font size=+1><b>DESCRIPTION </b></font><br> |
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| When a system call fails it returns –1 and records a null terminated |
| string describing the error in a per-process buffer. <i>Errstr</i> swaps |
| the contents of that buffer with the contents of the array <i>err</i>. |
| <i>Errstr</i> will write at most <i>nerr</i> bytes into <i>err</i>; if the per-process |
| error string does not fit, it is silently truncated at a UTF |
| character boundary. The returned string is NUL-terminated. Usually |
| <i>errstr</i> will be called with an empty string, but the exchange property |
| provides a mechanism for libraries to set the return value for |
| the next call to <i>errstr</i>. |
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| The per-process buffer is <tt><font size=+1>ERRMAX</font></tt> bytes long. Any error string |
| provided by the user will be truncated at <tt><font size=+1>ERRMAX−1</font></tt> bytes. <tt><font size=+1>ERRMAX</font></tt> |
| is defined in <tt><font size=+1><libc.h></font></tt>. |
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| If no system call has generated an error since the last call to |
| <i>errstr</i> with an empty string, the result is an empty string. |
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| The verb <tt><font size=+1>r</font></tt> in <a href="../man3/print.html"><i>print</i>(3)</a> calls <i>errstr</i> and outputs the error string. |
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| <i>Rerrstr</i> reads the error string but does not modify the per-process |
| buffer, so a subsequent <i>errstr</i> will recover the same string. |
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| <i>Werrstr</i> takes a <i>print</i> style format as its argument and uses it |
| to format a string to pass to <i>errstr</i>. The string returned from |
| <i>errstr</i> is discarded. |
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| The error string is maintained in parallel with the Unix error |
| number <i>errno</i>. Changing <i>errno</i> will reset the error string, and |
| changing the error string via <i>errstr</i> or <i>werrstr</i> will reset <i>errno</i>.<br> |
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| <p><font size=+1><b>SOURCE </b></font><br> |
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| <tt><font size=+1>/usr/local/plan9/src/lib9/errstr.c<br> |
| </font></tt> |
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| <p><font size=+1><b>DIAGNOSTICS </b></font><br> |
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| <i>Errstr</i> always returns 0.<br> |
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| </table> |
| <p><font size=+1><b>SEE ALSO </b></font><br> |
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| <a href="../man3/intro.html"><i>intro</i>(3)</a>, <a href="../man3/perror.html"><i>perror</i>(3)</a><br> |
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| <p><font size=+1><b>BUGS </b></font><br> |
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| The implementation sets <i>errno</i> to the (somewhat arbitrary) constant |
| 0x19283745 when the error string is valid. When <i>errno</i> is set to |
| other values, the error string is synthesized using <a href="../man3/strerror.html"><i>strerror</i>(3)</a>.<br> |
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