mirror of https://github.com/mkerrisk/man-pages
75 lines
2.6 KiB
Plaintext
75 lines
2.6 KiB
Plaintext
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "ERRNO" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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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 .
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