mirror of https://github.com/mkerrisk/man-pages
152 lines
3.6 KiB
Groff
152 lines
3.6 KiB
Groff
.\" Copyright (c) 1999 Andries Brouwer (aeb@cwi.nl)
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" 2003-11-15, aeb, added tmpnam_r
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.\"
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.TH TMPNAM 3 2003-11-15 "" "Linux Programmer's Manual"
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.SH NAME
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tmpnam, tmpnam_r \- create a name for a temporary file
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.SH SYNOPSIS
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.nf
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.B #include <stdio.h>
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.sp
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.BI "char *tmpnam(char *" s );
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.fi
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.SH DESCRIPTION
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The
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.BR tmpnam ()
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function returns a pointer to a string that is a valid filename,
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and such that a file with this name did not exist at some point
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in time, so that naive programmers may think it
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a suitable name for a temporary file.
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If the argument
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.I s
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is NULL this name is generated in an internal static buffer
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and may be overwritten by the next call to
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.BR tmpnam ().
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If
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.I s
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is not NULL, the name is copied to the character array (of length
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at least
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.IR L_tmpnam )
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pointed to by
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.I s
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and the value
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.I s
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is returned in case of success.
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.LP
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The pathname that is created, has a directory prefix
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.IR P_tmpdir .
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(Both
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.I L_tmpnam
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and
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.I P_tmpdir
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are defined in
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.IR <stdio.h> ,
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just like the
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.B TMP_MAX
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mentioned below.)
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.SH "RETURN VALUE"
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The
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.BR tmpnam ()
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function returns a pointer to a unique temporary
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filename, or NULL if a unique name cannot be generated.
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.SH ERRORS
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No errors are defined.
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.SH "CONFORMING TO"
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SVr4, 4.3BSD, C89, C99, POSIX.1-2001.
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.\" FIXME . Mar 08: The next POSIX.1 revisions marks tmpnam() obsolete.
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.SH NOTES
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The
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.BR tmpnam ()
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function generates a different string each time it is called,
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up to
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.B TMP_MAX
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times.
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If it is called more than
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.B TMP_MAX
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times,
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the behavior is implementation defined.
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.LP
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Although
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.BR tmpnam ()
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generates names that are difficult to guess,
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it is nevertheless possible that between the time that
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.BR tmpnam ()
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returns a pathname, and the time that the program opens it,
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another program might create that pathname using
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.BR open (2),
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or create it as a symbolic link.
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This can lead to security holes.
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To avoid such possibilities, use the
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.BR open (2)
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.B O_EXCL
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flag to open the pathname.
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Or better yet, use
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.BR mkstemp (3)
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or
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.BR tmpfile (3).
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.LP
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Portable applications that use threads cannot call
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.BR tmpnam ()
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with NULL parameter if either
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.B _POSIX_THREADS
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or
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.B _POSIX_THREAD_SAFE_FUNCTIONS
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is defined.
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.LP
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A POSIX draft proposed to use a function
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.BR tmpnam_r ()
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defined by
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.sp
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.nf
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.in +4n
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char *
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tmpnam_r(char *s)
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{
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return s ? tmpnam(s) : NULL;
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}
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.in
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.fi
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.sp
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apparently as a warning not to use NULL.
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A few systems implement it.
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To get a glibc prototype for this function,
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define
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.B _SVID_SOURCE
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or
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.B _BSD_SOURCE
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before including
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.IR <stdio.h> .
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.SH BUGS
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Never use this function.
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Use
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.BR mkstemp (3)
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or
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.BR tmpfile (3)
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instead.
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.SH "SEE ALSO"
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.BR mkstemp (3),
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.BR mktemp (3),
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.BR tempnam (3),
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.BR tmpfile (3)
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