| .\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de) |
| .\" and Copyright (C) 2017 Michael Kerrisk <mtk.manpages@gmail.com> |
| .\" |
| .\" %%%LICENSE_START(VERBATIM) |
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| .\" manual under the conditions for verbatim copying, provided that the |
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| .\" Since the Linux kernel and libraries are constantly changing, this |
| .\" manual page may be incorrect or out-of-date. The author(s) assume no |
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| .\" Modified Wed Jul 28 11:12:26 1993 by Rik Faith (faith@cs.unc.edu) |
| .\" |
| .\" FIXME Probably all of the following should be documented: |
| .\" _PC_SYNC_IO, |
| .\" _PC_ASYNC_IO, |
| .\" _PC_PRIO_IO, |
| .\" _PC_SOCK_MAXBUF, |
| .\" _PC_FILESIZEBITS, |
| .\" _PC_REC_INCR_XFER_SIZE, |
| .\" _PC_REC_MAX_XFER_SIZE, |
| .\" _PC_REC_MIN_XFER_SIZE, |
| .\" _PC_REC_XFER_ALIGN, |
| .\" _PC_ALLOC_SIZE_MIN, |
| .\" _PC_SYMLINK_MAX, |
| .\" _PC_2_SYMLINKS |
| .\" |
| .TH FPATHCONF 3 2017-07-13 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| fpathconf, pathconf \- get configuration values for files |
| .SH SYNOPSIS |
| .nf |
| .B #include <unistd.h> |
| .PP |
| .BI "long fpathconf(int " fd ", int " name ); |
| .BI "long pathconf(const char *" path ", int " name ); |
| .fi |
| .SH DESCRIPTION |
| .BR fpathconf () |
| gets a value for the configuration option |
| .I name |
| for the open file descriptor |
| .IR fd . |
| .PP |
| .BR pathconf () |
| gets a value for configuration option |
| .I name |
| for the filename |
| .IR path . |
| .PP |
| The corresponding macros defined in |
| .I <unistd.h> |
| are minimum values; if an application wants to take advantage of values |
| which may change, a call to |
| .BR fpathconf () |
| or |
| .BR pathconf () |
| can be made, which may yield more liberal results. |
| .PP |
| Setting |
| .I name |
| equal to one of the following constants returns the following |
| configuration options: |
| .TP |
| .B _PC_LINK_MAX |
| The maximum number of links to the file. |
| If |
| .I fd |
| or |
| .I path |
| refer to a directory, then the value applies to the whole directory. |
| The corresponding macro is |
| .BR _POSIX_LINK_MAX . |
| .TP |
| .B _PC_MAX_CANON |
| The maximum length of a formatted input line, where |
| .I fd |
| or |
| .I path |
| must refer to a terminal. |
| The corresponding macro is |
| .BR _POSIX_MAX_CANON . |
| .TP |
| .B _PC_MAX_INPUT |
| The maximum length of an input line, where |
| .I fd |
| or |
| .I path |
| must refer to a terminal. |
| The corresponding macro is |
| .BR _POSIX_MAX_INPUT . |
| .TP |
| .B _PC_NAME_MAX |
| The maximum length of a filename in the directory |
| .I path |
| or |
| .IR fd |
| that the process is allowed to create. |
| The corresponding macro is |
| .BR _POSIX_NAME_MAX . |
| .TP |
| .B _PC_PATH_MAX |
| The maximum length of a relative pathname when |
| .I path |
| or |
| .I fd |
| is the current working directory. |
| The corresponding macro is |
| .BR _POSIX_PATH_MAX . |
| .TP |
| .B _PC_PIPE_BUF |
| The maximum number of bytes that can be written atomically to a pipe of FIFO. |
| For |
| .BR fpathconf (), |
| .I fd |
| should refer to a pipe or FIFO. |
| For |
| .BR fpathconf (), |
| .I path |
| should refer to a FIFO or a directory; in the latter case, |
| the returned value corresponds to FIFOs created in that directory. |
| The corresponding macro is |
| .BR _POSIX_PIPE_BUF . |
| .TP |
| .B _PC_CHOWN_RESTRICTED |
| This returns a positive value if the use of |
| .BR chown (2) |
| and |
| .BR fchown (2) |
| for changing a file's user ID is restricted to a process |
| with appropriate privileges, |
| and changing a file's group ID to a value other than the process's |
| effective group ID or one of its supplementary group IDs |
| is restricted to a process with appropriate privileges. |
| According to POSIX.1, |
| this variable shall always be defined with a value other than \-1. |
| The corresponding macro is |
| .BR _POSIX_CHOWN_RESTRICTED . |
| .IP |
| If |
| .I fd |
| or |
| .I path |
| refers to a directory, |
| then the return value applies to all files in that directory. |
| .TP |
| .B _PC_NO_TRUNC |
| This returns nonzero if accessing filenames longer than |
| .B _POSIX_NAME_MAX |
| generates an error. |
| The corresponding macro is |
| .BR _POSIX_NO_TRUNC . |
| .TP |
| .B _PC_VDISABLE |
| This returns nonzero if special character processing can be disabled, where |
| .I fd |
| or |
| .I path |
| must refer to a terminal. |
| .SH RETURN VALUE |
| The return value of these functions is one of the following: |
| .IP * 3 |
| On error, \-1 is returned and |
| .I errno |
| is set to indicate the cause of the error |
| (for example, |
| .BR EINVAL , |
| indicating that |
| .I name |
| is invalid). |
| .IP * |
| If |
| .I name |
| corresponds to a maximum or minimum limit, and that limit is indeterminate, |
| \-1 is returned and |
| .I errno |
| is not changed. |
| (To distinguish an indeterminate limit from an error, set |
| .I errno |
| to zero before the call, and then check whether |
| .I errno |
| is nonzero when \-1 is returned.) |
| .IP * |
| If |
| .I name |
| corresponds to an option, |
| a positive value is returned if the option is supported, |
| and \-1 is returned if the option is not supported. |
| .IP * |
| Otherwise, |
| the current value of the option or limit is returned. |
| This value will not be more restrictive than |
| the corresponding value that was described to the application in |
| .I <unistd.h> |
| or |
| .I <limits.h> |
| when the application was compiled. |
| .SH ERRORS |
| .TP |
| .B EACCES |
| .RB ( pathconf ()) |
| Search permission is denied for one of the directories in the path prefix of |
| .IR path . |
| .TP |
| .B EBADF |
| .RB ( fpathconf ()) |
| .I fd |
| is not a valid file descriptor. |
| .TP |
| .B EINVAL |
| .I name |
| is invalid. |
| .TP |
| .B EINVAL |
| The implementation does not support an association of |
| .I name |
| with the specified file. |
| .TP |
| .B ELOOP |
| .RB ( pathconf ()) |
| Too many symbolic links were encountered while resolving |
| .IR path . |
| .TP |
| .B ENAMETOOLONG |
| .RB ( pathconf ()) |
| .I path |
| is too long. |
| .TP |
| .B ENOENT |
| .RB ( pathconf ()) |
| A component of |
| .I path |
| does not exist, or |
| .I path |
| is an empty string. |
| .TP |
| .B ENOTDIR |
| .RB ( pathconf ()) |
| A component used as a directory in |
| .I path |
| is not in fact a directory. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .TS |
| allbox; |
| lbw23 lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR fpathconf (), |
| .BR pathconf () |
| T} Thread safety MT-Safe |
| .TE |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008. |
| .SH NOTES |
| Files with name lengths longer than the value returned for |
| .I name |
| equal to |
| .B _PC_NAME_MAX |
| may exist in the given directory. |
| .PP |
| Some returned values may be huge; they are not suitable for allocating |
| memory. |
| .SH SEE ALSO |
| .BR getconf (1), |
| .BR open (2), |
| .BR statfs (2), |
| .BR confstr (3), |
| .BR sysconf (3) |