diff options
Diffstat (limited to 'manual/filesys.texi')
| -rw-r--r-- | manual/filesys.texi | 77 |
1 files changed, 48 insertions, 29 deletions
diff --git a/manual/filesys.texi b/manual/filesys.texi index d2afe8623f..e269663e70 100644 --- a/manual/filesys.texi +++ b/manual/filesys.texi @@ -261,7 +261,7 @@ are declared in the header file @file{dirent.h}. @comment dirent.h @comment POSIX.1 @deftp {Data Type} DIR -The @code{DIR} data type represents a directory stream. +The @code{DIR} data type represents a directory stream. @end deftp You shouldn't ever allocate objects of the @code{struct dirent} or @@ -333,7 +333,7 @@ The @var{dirstream} argument is not valid. @comment POSIX.1 @deftypefun int closedir (DIR *@var{dirstream}) This function closes the directory stream @var{dirstream}. It returns -@code{0} on success and @code{-1} on failure. +@code{0} on success and @code{-1} on failure. The following @code{errno} error conditions are defined for this function: @@ -443,7 +443,7 @@ following @code{errno} error conditions are defined for this function: @item EACCES You are not allowed to write the directory in which the new link is to be written. -@ignore +@ignore Some implementations also require that the existing file be accessible by the caller, and use this error to report failure for that reason. @end ignore @@ -627,7 +627,7 @@ The function @code{unlink} is declared in the header file @file{unistd.h}. This function returns @code{0} on successful completion, and @code{-1} on error. In addition to the usual file name errors -(@pxref{File Name Errors}), the following @code{errno} error conditions are +(@pxref{File Name Errors}), the following @code{errno} error conditions are defined for this function: @table @code @@ -672,7 +672,7 @@ are two additional @code{errno} error conditions defined for @table @code @item ENOTEMPTY @itemx EEXIST -The directory to be deleted is not empty. +The directory to be deleted is not empty. @end table These two error codes are synonymous; some systems use one, and some use @@ -851,20 +851,20 @@ This section contains information about how you can inquire about and modify these attributes of files. @menu -* Attribute Meanings:: The names of the file attributes, +* Attribute Meanings:: The names of the file attributes, and what their values mean. * Reading Attributes:: How to read the attributes of a file. * Testing File Type:: Distinguishing ordinary files, - directories, links... + directories, links... * File Owner:: How ownership for new files is determined, and how to change it. * Permission Bits:: How information about a file's access - mode is stored. + mode is stored. * Access Permission:: How the system decides who can access a file. * Setting Permissions:: How permissions for new files are assigned, and how to change them. * Testing File Access:: How to find out if your process can - access a file. + access a file. * File Times:: About the time attributes of a file. @end menu @@ -1079,7 +1079,7 @@ a socket, and so on. For information about the access permission, @ref{Permission Bits}. There are two predefined ways you can access the file type portion of -the file mode. First of all, for each type of file, there is a +the file mode. First of all, for each type of file, there is a @dfn{predicate macro} which examines a file mode value and returns true or false---is the file of that type, or not. Secondly, you can mask out the rest of the file mode to get just a file type code. @@ -1260,7 +1260,7 @@ bits may not be appropriate for the new owner.) The other file permission bits are not changed. The return value is @code{0} on success and @code{-1} on failure. -In addition to the usual file name errors (@pxref{File Name Errors}), +In addition to the usual file name errors (@pxref{File Name Errors}), the following @code{errno} error conditions are defined for this function: @table @code @@ -1421,7 +1421,7 @@ This is equivalent to @samp{(S_IROTH | S_IWOTH | S_IXOTH)}. @comment POSIX @item S_ISUID @vindex S_ISUID -This is the set-user-ID on execute bit, usually 04000. +This is the set-user-ID on execute bit, usually 04000. @xref{How Change Persona}. @comment sys/stat.h @@ -1462,7 +1462,7 @@ arose since the last run. On some modern systems where the sticky bit has no useful meaning for an executable file, you cannot set the bit at all for a non-directory. -If you try, @code{chmod} fails with @code{EFTYPE}; +If you try, @code{chmod} fails with @code{EFTYPE}; @pxref{Setting Permissions}. Some systems (particularly SunOS) have yet another use for the sticky @@ -1527,7 +1527,7 @@ The bits that are set in the file creation mask identify permissions that are always to be disabled for newly created files. For example, if you set all the ``other'' access bits in the mask, then newly created files are not accessible at all to processes in the ``other'' -category, even if the @var{mode} argument specified to the creation +category, even if the @var{mode} argument specified to the creation function would permit such access. In other words, the file creation mask is the complement of the ordinary access permissions you want to grant. @@ -1671,7 +1671,7 @@ files off-limits to ordinary users---for example, to modify @file{/etc/passwd}. Programs designed to be run by ordinary users but access such files use the setuid bit feature so that they always run with @code{root} as the effective user ID. - + Such a program may also access files specified by the user, files which conceptually are being accessed explicitly by the user. Since the program runs as @code{root}, it has permission to access whatever file @@ -1776,7 +1776,7 @@ Argument that means, test for existence of the file. Each file has three timestamps associated with it: its access time, its modification time, and its attribute modification time. These correspond to the @code{st_atime}, @code{st_mtime}, and @code{st_ctime} -members of the @code{stat} structure; see @ref{File Attributes}. +members of the @code{stat} structure; see @ref{File Attributes}. All of these times are represented in calendar time format, as @code{time_t} objects. This data type is defined in @file{time.h}. @@ -1832,7 +1832,7 @@ named @var{filename}. If @var{times} is a null pointer, then the access and modification times of the file are set to the current time. Otherwise, they are set to the values from the @code{actime} and @code{modtime} members (respectively) -of the @code{utimbuf} structure pointed at by @var{times}. +of the @code{utimbuf} structure pointed at by @var{times}. The attribute modification time for the file is set to the current time in either case (since changing the timestamps is itself a modification @@ -1938,12 +1938,14 @@ this file, you must remove the old file explicitly first. If you need to use a temporary file in your program, you can use the @code{tmpfile} function to open it. Or you can use the @code{tmpnam} -function make a name for a temporary file and then open it in the usual -way with @code{fopen}. +(better: @code{tmpnam_r}) function make a name for a temporary file and +then open it in the usual way with @code{fopen}. The @code{tempnam} function is like @code{tmpnam} but lets you choose what directory temporary files will go in, and something about what -their file names will look like. +their file names will look like. Important for multi threaded programs +is that @code{tempnam} is reentrant while @code{tmpnam} is not since it +returns a pointer to a static buffer. These facilities are declared in the header file @file{stdio.h}. @pindex stdio.h @@ -1956,6 +1958,8 @@ calling @code{fopen} with mode @code{"wb+"}. The file is deleted automatically when it is closed or when the program terminates. (On some other ANSI C systems the file may fail to be deleted if the program terminates abnormally). + +This function is reentrant. @end deftypefun @comment stdio.h @@ -1964,14 +1968,26 @@ terminates abnormally). This function constructs and returns a file name that is a valid file name and that does not name any existing file. If the @var{result} argument is a null pointer, the return value is a pointer to an internal -static string, which might be modified by subsequent calls. Otherwise, -the @var{result} argument should be a pointer to an array of at least -@code{L_tmpnam} characters, and the result is written into that array. - -It is possible for @code{tmpnam} to fail if you call it too many times. -This is because the fixed length of a temporary file name gives room for -only a finite number of different names. If @code{tmpnam} fails, it -returns a null pointer. +static string, which might be modified by subsequent calls and therefore +makes this function non-reentrant. Otherwise, the @var{result} argument +should be a pointer to an array of at least @code{L_tmpnam} characters, +and the result is written into that array. + +It is possible for @code{tmpnam} to fail if you call it too many times +without removing previously created files. This is because the fixed +length of a temporary file name gives room for only a finite number of +different names. If @code{tmpnam} fails, it returns a null pointer. +@end deftypefun + +@comment stdio.h +@comment GNU +@deftypefun {char *} tmpnam_r (char *@var{result}) +This function is nearly identical to the @code{tmpnam} function. But it +does not allow @var{result} to be a null pointer. In the later case a +null pointer is returned. + +This function is reentrant because the non-reentrant situation of +@code{tmpnam} cannot happen here. @end deftypefun @comment stdio.h @@ -2006,13 +2022,16 @@ prefix for the file name. The return value is a string newly allocated with @code{malloc}; you should release its storage with @code{free} when it is no longer needed. +Because the string is dynamically allocated this function is reentrant. + The directory prefix for the temporary file name is determined by testing each of the following, in sequence. The directory must exist and be writable. @itemize @bullet @item -The environment variable @code{TMPDIR}, if it is defined. +The environment variable @code{TMPDIR}, if it is defined. For security +reasons this only happens if the program is not SUID or SGID enabled. @item The @var{dir} argument, if it is not a null pointer. |