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by Francesco Paolo Lovergine
rules: linking manpages-posix not manpages. |
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved |
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by Francesco Paolo Lovergine
* Alligned to linux main manpages edition. |
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.TH "ERRNO" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" |
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by Francesco Paolo Lovergine
rules: linking manpages-posix not manpages. |
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.\" errno |
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.SH NAME |
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errno \- error return value
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.SH SYNOPSIS |
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.LP
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\fB#include <errno.h>\fP |
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.SH DESCRIPTION |
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.LP
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The lvalue \fIerrno\fP is used by many functions to return error values. |
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.LP
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Many functions provide an error number in \fIerrno\fP, which has type |
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\fBint\fP and is defined in \fI<errno.h>\fP. The value of \fIerrno\fP |
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shall be defined only after a call to a function |
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for which it is explicitly stated to be set and until it is changed |
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by the next function call or if the application assigns it a |
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value. The value of \fIerrno\fP should only be examined when it is |
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indicated to be valid by a function's return value. |
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Applications shall obtain the definition of \fIerrno\fP by the inclusion |
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of \fI<errno.h>\fP. No function in this volume of IEEE\ Std\ 1003.1-2001 |
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shall set |
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\fIerrno\fP to 0. |
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.LP
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It is unspecified whether \fIerrno\fP is a macro or an identifier |
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declared with external linkage. If a macro definition is |
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suppressed in order to access an actual object, or a program defines |
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an identifier with the name \fIerrno\fP, the behavior is |
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undefined. |
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.LP
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The symbolic values stored in \fIerrno\fP are documented in the ERRORS |
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sections on all relevant pages. |
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.SH RETURN VALUE |
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.LP
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None. |
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.SH ERRORS |
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.LP
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None. |
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.LP
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\fIThe following sections are informative.\fP |
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.SH EXAMPLES |
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.LP
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None. |
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.SH APPLICATION USAGE |
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.LP
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Previously both POSIX and X/Open documents were more restrictive than |
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the ISO\ C standard in that they required \fIerrno\fP |
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to be defined as an external variable, whereas the ISO\ C standard
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required only that \fIerrno\fP be defined as a modifiable |
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lvalue with type \fBint\fP. |
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.LP
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An application that needs to examine the value of \fIerrno\fP to determine |
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the error should set it to 0 before a function call, |
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then inspect it before a subsequent function call. |
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.SH RATIONALE |
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.LP
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None. |
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.SH FUTURE DIRECTIONS |
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.LP
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None. |
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.SH SEE ALSO |
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.LP
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\fIError Numbers\fP , the Base Definitions volume of IEEE\ Std\ 1003.1-2001, |
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\fI<errno.h>\fP |
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.SH COPYRIGHT |
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Portions of this text are reprinted and reproduced in electronic form |
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology |
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-- Portable Operating System Interface (POSIX), The Open Group Base |
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of |
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Electrical and Electronics Engineers, Inc and The Open Group. In the |
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event of any discrepancy between this version and the original IEEE and |
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The Open Group Standard, the original IEEE and The Open Group Standard |
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is the referee document. The original Standard can be obtained online at |
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http://www.opengroup.org/unix/online.html . |