alphasort.3p (6827B)
- '\" et
- .TH ALPHASORT "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
- .\"
- .SH PROLOG
- This manual page is part of the POSIX Programmer's Manual.
- The Linux implementation of this interface may differ (consult
- the corresponding Linux manual page for details of Linux behavior),
- or the interface may not be implemented on Linux.
- .\"
- .SH NAME
- alphasort, scandir
- \(em scan a directory
- .SH SYNOPSIS
- .LP
- .nf
- #include <dirent.h>
- .P
- int alphasort(const struct dirent **\fId1\fP, const struct dirent **\fId2\fP);
- int scandir(const char *\fIdir\fP, struct dirent ***\fInamelist\fP,
- int (*\fIsel\fP)(const struct dirent *),
- int (*\fIcompar\fP)(const struct dirent **, const struct dirent **));
- .fi
- .SH DESCRIPTION
- The
- \fIalphasort\fR()
- function can be used as the comparison function for the
- \fIscandir\fR()
- function to sort the directory entries,
- .IR d1
- and
- .IR d2 ,
- into alphabetical order. Sorting happens as if by calling the
- \fIstrcoll\fR()
- function on the
- .IR d_name
- element of the
- .BR dirent
- structures passed as the two parameters. If the
- \fIstrcoll\fR()
- function fails, the return value of
- \fIalphasort\fR()
- is unspecified.
- .P
- The
- \fIalphasort\fR()
- function shall not change the setting of
- .IR errno
- if successful. Since no return value is reserved to indicate an error,
- an application wishing to check for error situations should set
- .IR errno
- to 0, then call
- \fIalphasort\fR(),
- then check
- .IR errno .
- .P
- The
- \fIscandir\fR()
- function shall scan the directory
- .IR dir ,
- calling the function referenced by
- .IR sel
- on each directory entry. Entries for which the function referenced by
- .IR sel
- returns non-zero shall be stored in strings allocated as if by
- a call to
- \fImalloc\fR(),
- and sorted as if by a call to
- \fIqsort\fR()
- with the comparison function
- .IR compar ,
- except that
- .IR compar
- need not provide total ordering. The strings are collected in
- array
- .IR namelist
- which shall be allocated as if by a call to
- \fImalloc\fR().
- If
- .IR sel
- is a null pointer, all entries shall be selected.
- If the comparison function
- .IR compar
- does not provide total ordering, the order in which the directory
- entries are stored is unspecified.
- .SH "RETURN VALUE"
- Upon successful completion, the
- \fIalphasort\fR()
- function shall return an integer greater than, equal to, or less than 0,
- according to whether the name of the directory entry pointed to by
- .IR d1
- is lexically greater than, equal to, or less than the directory pointed
- to by
- .IR d2
- when both are interpreted as appropriate to the current locale. There
- is no return value reserved to indicate an error.
- .P
- Upon successful completion, the
- \fIscandir\fR()
- function shall return the number of entries in the array and a pointer
- to the array through the parameter
- .IR namelist .
- Otherwise, the
- \fIscandir\fR()
- function shall return \-1.
- .SH ERRORS
- The
- \fIscandir\fR()
- function shall fail if:
- .TP
- .BR EACCES
- Search permission is denied for the component of the path prefix of
- .IR dir
- or read permission is denied for
- .IR dir .
- .TP
- .BR ELOOP
- A loop exists in symbolic links encountered during resolution of the
- .IR dir
- argument.
- .TP
- .BR ENAMETOOLONG
- .br
- The length of a component of a pathname is longer than
- {NAME_MAX}.
- .TP
- .BR ENOENT
- A component of
- .IR dir
- does not name an existing directory or
- .IR dir
- is an empty string.
- .TP
- .BR ENOMEM
- Insufficient storage space is available.
- .TP
- .BR ENOTDIR
- A component of
- .IR dir
- names an existing file that is neither a directory nor a symbolic link
- to a directory.
- .TP
- .BR EOVERFLOW
- One of the values to be returned or passed to a callback function cannot
- be represented correctly.
- .P
- The
- \fIscandir\fR()
- function may fail if:
- .TP
- .BR ELOOP
- More than
- {SYMLOOP_MAX}
- symbolic links were encountered during resolution of the
- .IR dir
- argument.
- .TP
- .BR EMFILE
- All file descriptors available to the process are currently open.
- .TP
- .BR ENAMETOOLONG
- .br
- The length of a pathname exceeds
- {PATH_MAX},
- or pathname resolution of a symbolic link produced an intermediate
- result with a length that exceeds
- {PATH_MAX}.
- .TP
- .BR ENFILE
- Too many files are currently open in the system.
- .LP
- .IR "The following sections are informative."
- .SH EXAMPLES
- An example to print the files in the current directory:
- .sp
- .RS 4
- .nf
- #include <dirent.h>
- #include <stdio.h>
- #include <stdlib.h>
- \&...
- struct dirent **namelist;
- int i,n;
- .P
- n = scandir(".", &namelist, 0, alphasort);
- if (n < 0)
- perror("scandir");
- else {
- for (i = 0; i < n; i++) {
- printf("%s\en", namelist[i]->d_name);
- free(namelist[i]);
- }
- }
- free(namelist);
- \&...
- .fi
- .P
- .RE
- .SH "APPLICATION USAGE"
- If
- .IR dir
- contains filenames that do not form character strings, or which contain
- characters outside the domain of the collating sequence of the current
- locale, the
- \fIalphasort\fR()
- function need not provide a total ordering. This condition is not possible
- if all filenames within the directory consist only of characters from
- the portable filename character set.
- .P
- The
- \fIscandir\fR()
- function may allocate dynamic storage during its operation. If
- \fIscandir\fR()
- is forcibly terminated, such as by
- \fIlongjmp\fR()
- or
- \fIsiglongjmp\fR()
- being executed by the function pointed to by
- .IR sel
- or
- .IR compar ,
- or by an interrupt routine,
- \fIscandir\fR()
- does not have a chance to free that storage, so it remains permanently
- allocated. A safe way to handle interrupts is to store the fact that
- an interrupt has occurred, then wait until
- \fIscandir\fR()
- returns to act on the interrupt.
- .P
- For functions that allocate memory as if by
- \fImalloc\fR(),
- the application should release such memory when it is no longer
- required by a call to
- \fIfree\fR().
- For
- \fIscandir\fR(),
- this is
- .IR namelist
- (including all of the individual strings in
- .IR namelist ).
- .SH RATIONALE
- None.
- .SH "FUTURE DIRECTIONS"
- None.
- .SH "SEE ALSO"
- .IR "\fIqsort\fR\^(\|)",
- .IR "\fIstrcoll\fR\^(\|)"
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "\fB<dirent.h>\fP"
- .\"
- .SH COPYRIGHT
- Portions of this text are reprinted and reproduced in electronic form
- from IEEE Std 1003.1-2017, Standard for Information Technology
- -- Portable Operating System Interface (POSIX), The Open Group Base
- Specifications Issue 7, 2018 Edition,
- Copyright (C) 2018 by the Institute of
- Electrical and Electronics Engineers, Inc and The Open Group.
- In the event of any discrepancy between this version and the original IEEE and
- The Open Group Standard, the original IEEE and The Open Group Standard
- is the referee document. The original Standard can be obtained online at
- http://www.opengroup.org/unix/online.html .
- .PP
- Any typographical or formatting errors that appear
- in this page are most likely
- to have been introduced during the conversion of the source files to
- man page format. To report such errors, see
- https://www.kernel.org/doc/man-pages/reporting_bugs.html .