Ftw routines
Jeff Beadles
jeff at onion.pdx.com
Mon Dec 3 16:04:07 AEST 1990
Someone asked in alt.sources.wanted for a set of ftw() routines. Here's what
I received when I asked for this a year ago...
Path: uunet!husc6!hao!oddjob!gargoyle!ihnp4!cbosgd!mandrill!hal!ncoast!allbery
From: rsalz at pebbles.bbn.com
Newsgroups: comp.sources.misc
Subject: scandir, ftw REDUX
Message-ID: <6943 at ncoast.UUCP>
Date: 1 Jan 88 00:47:01 GMT
Sender: allbery at ncoast.UUCP
Lines: 505
Approved: allbery at ncoast.UUCP
X-Archive: comp.sources.misc/8712/15
Forget my previous message -- I just decided for completeness's sake to
implement the SysV ftw(3) routine, too.
To repeat, these are public-domain implementations of the SystemV ftw()
routine, the BSD scandir() and alphasort() routines, and documentation for
same. The FTW manpage could be more readable, but so it goes.
Anyhow, feel free to post these, and incorporate them into your existing
packages. I have readdir() routiens for MSDOS and the Amiga if anyone
wants them, and should have them for VMS by the end of January; let me
know if you want copies.
Yours in filesystems,
/r$
Anyhow, feel free to post
#! /bin/sh
# This is a shell archive. Remove anything before this line, then unpack
# it by saving it into a file and typing "sh file". To overwrite existing
# files, type "sh file -c". You can also feed this as standard input via
# unshar, or by typing "sh <file", e.g.. If this archive is complete, you
# will see the following message at the end:
# "End of shell archive."
# Contents: alphasort.c ftw.3 ftw.c ftw.h scandir.3 scandir.c
# Wrapped by djm at twiddle on Sat Dec 30 14:14:49 1989
PATH=/bin:/usr/bin:/usr/ucb ; export PATH
if test -f 'alphasort.c' -a "${1}" != "-c" ; then
echo shar: Will not clobber existing file \"'alphasort.c'\"
else
echo shar: Extracting \"'alphasort.c'\" \(381 characters\)
sed "s/^X//" >'alphasort.c' <<'END_OF_FILE'
X/*
X** ALPHASORT
X** Trivial sorting predicate for scandir; puts entries in alphabetical order.
X*/
X
X#include <sys/types.h>
X#include <sys/dir.h>
X
X#ifdef RCSID
Xstatic char RCS[] = "$Header: alphasort.c,v 1.1 87/12/29 21:35:59 rsalz Exp $";
X#endif /* RCSID */
X
Xint
Xalphasort(d1, d2)
X struct direct **d1;
X struct direct **d2;
X{
X return strcmp(d1[0]->d_name, d2[0]->d_name);
X}
END_OF_FILE
if test 381 -ne `wc -c <'alphasort.c'`; then
echo shar: \"'alphasort.c'\" unpacked with wrong size!
fi
# end of 'alphasort.c'
fi
if test -f 'ftw.3' -a "${1}" != "-c" ; then
echo shar: Will not clobber existing file \"'ftw.3'\"
else
echo shar: Extracting \"'ftw.3'\" \(2139 characters\)
sed "s/^X//" >'ftw.3' <<'END_OF_FILE'
X.TH FTW 3
X.\" $Header: ftw.3,v 1.1 87/12/29 21:34:29 rsalz Exp $
X.SH NAME
Xftw \- walk a file tree
X.SH SYNOPSIS
X.ft B
X.nf
X#include <ftw.h>
X
Xint
Xftw(directory, funcptr, depth)
X char *directory;
X int (*funcptr)();
X int depth;
X
X#include <sys/stat.h>
X
Xint
Xfuncptr(item, sb, flag)
X char *item;
X struct stat *sb;
X int flag;
X.fi
X.ft R
X.SH DESCRIPTION
X.I Ftw
Xwalks through the directory tree starting from the indicated
X.IR path .
XFor every entry it finds in the tree, it calls the user-supplied
X.I funcptr
Xwith the calling sequence given in the synopsis above.
XThe first argument is the full pathname of the entry (rooted from
Xthe
X.I directory
Xparameter given to
X.IR ftw );
Xthe second argument is a pointer to the
X.IR stat (2)
Xstructure for the entry;
Xand the third argument is one of the #define's in the header file.
XThis value will be one of the following:
X.RS
X.ta \w'FTW_DNR 'u
X.nf
XFTW_F Item is a normal file
XFTW_D Item is a directory
XFTW_NS The stat failed on the item
XFTW_DNR Item is a directory which can't be read
X.fi
X.RE
XNote, however, that FTW_F is a misnomer; anything other than directories
Xare (e.g., symbolic links) get the FTW_F tag.
X.PP
X.I Ftw
Xrecursively calls itself when it encounters a directory.
XTo avoid using up all a program's file descriptors, the
X.I depth
Xargument specifies the number of simultaneous open directories to maintain.
XWhen the depth is exceeded, the routine will become noticeably
Xslower because directories are closed in ``most-recently-used'' order.
X.PP
XTo stop the tree walk, the user-supplied function should return a
Xnon\-zero value; this value will become the return value of
X.IR ftw .
XOtherwise,
X.I ftw
Xwill continue until it has scanned the entire tree, in which case it will
Xreturn zero, or until it hits an error such as a
X.IR malloc (3)
Xfailure, in which case it will return \-1.
X.PP
XBecause
X.I ftw
Xuses dynamic data structures, the only safe way to exit out of a tree
Xwalk is to return a non-zero value.
XTo handle interrupts, for example, mark that the interrupt occured
Xand return a non\-zero value\(em don't use
X.I longjmp (3)
Xunless the program is going to terminate.
X.SH SEE ALSO
Xstat(2)
END_OF_FILE
if test 2139 -ne `wc -c <'ftw.3'`; then
echo shar: \"'ftw.3'\" unpacked with wrong size!
fi
# end of 'ftw.3'
fi
if test -f 'ftw.c' -a "${1}" != "-c" ; then
echo shar: Will not clobber existing file \"'ftw.c'\"
else
echo shar: Extracting \"'ftw.c'\" \(2487 characters\)
sed "s/^X//" >'ftw.c' <<'END_OF_FILE'
X/*
X** FTW
X** Walk a directory hierarchy from a given point, calling a user-supplied
X** function at each thing we find. If we go below a specified depth,
X** recycle file descriptors.
X*/
X
X#include <stdio.h>
X#include <sys/types.h>
X#include <sys/stat.h>
X#include <sys/dir.h>
X#include <ftw.h>
X
X#ifdef RCSID
Xstatic char RCS[] = "$Header: ftw.c,v 1.1 87/12/29 21:38:52 rsalz Exp $";
X#endif /* RCSID */
X
X#define EQ(a, b) (strcmp((a), (b)) == 0)
X
Xextern char *malloc();
Xextern char *strcpy();
X
Xint
Xftw(directory, funcptr, depth)
X char *directory;
X int (*funcptr)();
X int depth;
X{
X register DIR *dirp;
X struct direct *entp;
X struct stat stats;
X register char *p;
X register int i;
X long seekpoint;
X char *fullpath;
X
X /* If can't stat, tell the user so. */
X if (stat(directory, &stats) < 0)
X return (*funcptr)(directory, &stats, FTW_NS);
X
X /* If it's not a directory, call the user's function. */
X if ((stats.st_mode & S_IFMT) != S_IFDIR)
X /* Saying "FTW_F" here is lying; what if this is a symlink? */
X return (*funcptr)(directory, &stats, FTW_F);
X
X /* Open directory; if we can't, tell the user so. */
X dirp = opendir(directory);
X if (dirp == NULL)
X return (*funcptr)(directory, &stats, FTW_DNR);
X
X /* See if user wants to go further. */
X i = (*funcptr)(directory, &stats, FTW_D);
X if (i) {
X closedir(dirp);
X return i;
X }
X
X /* Get ready to hold the full paths. */
X i = strlen(directory);
X fullpath = malloc(i + 1 + MAXNAMLEN + 1);
X if (fullpath == NULL) {
X closedir(dirp);
X return -1;
X }
X (void)strcpy(fullpath, directory);
X p = &fullpath[i];
X if (i && p[-1] != '/')
X *p++ = '/';
X
X /* Read all entries in the directory.. */
X while (entp = readdir(dirp))
X if (!EQ(entp->d_name, ".") && !EQ(entp->d_name, "..")) {
X if (depth <= 1) {
X /* Going too deep; checkpoint and close this directory. */
X seekpoint = telldir(dirp);
X closedir(dirp);
X dirp = NULL;
X }
X
X /* Process the file. */
X (void)strcpy(p, entp->d_name);
X i = ftw(fullpath, funcptr, depth - 1);
X if (i) {
X /* User's finished; clean up. */
X free(fullpath);
X if (dirp)
X closedir(dirp);
X return i;
X }
X
X /* Reopen the directory if necessary. */
X if (dirp == NULL) {
X dirp = opendir(directory);
X if (dirp == NULL) {
X free(fullpath);
X return -1;
X }
X seekdir(dirp, seekpoint);
X }
X }
X
X /* Clean up. */
X free(fullpath);
X closedir(dirp);
X return 0;
X}
END_OF_FILE
if test 2487 -ne `wc -c <'ftw.c'`; then
echo shar: \"'ftw.c'\" unpacked with wrong size!
fi
# end of 'ftw.c'
fi
if test -f 'ftw.h' -a "${1}" != "-c" ; then
echo shar: Will not clobber existing file \"'ftw.h'\"
else
echo shar: Extracting \"'ftw.h'\" \(350 characters\)
sed "s/^X//" >'ftw.h' <<'END_OF_FILE'
X/*
X** <FTW.H>
X** Header values for the third parameter to the user-supplied function
X** for ftw().
X**
X** $Header: ftw.h,v 1.1 87/12/29 21:34:34 rsalz Exp $
X*/
X
X#define FTW_F 0 /* A normal file */
X#define FTW_D 1 /* A directory */
X#define FTW_DNR 2 /* Something opendir(3) failed on */
X#define FTW_NS 3 /* Something stat(2) failed on */
END_OF_FILE
if test 350 -ne `wc -c <'ftw.h'`; then
echo shar: \"'ftw.h'\" unpacked with wrong size!
fi
# end of 'ftw.h'
fi
if test -f 'scandir.3' -a "${1}" != "-c" ; then
echo shar: Will not clobber existing file \"'scandir.3'\"
else
echo shar: Extracting \"'scandir.3'\" \(2350 characters\)
sed "s/^X//" >'scandir.3' <<'END_OF_FILE'
X.TH SCANDIR 3
X.\" $Header: scandir.3,v 1.1 87/12/29 21:35:54 rsalz Exp $
X.SH NAME
Xscandir, alphasort \- scan a directory
X.SH SYNOPSIS
X.nf
X.ft B
X#include <sys/types.h>
X#include <sys/dir.h>
X
Xint
Xscandir(name, list, selector, sorter)
X.in +4n
Xchar *name;
Xstruct direct ***list;
Xint (*selector)();
Xint (*sorter)();
X.in -4n
X
Xint
Xalphasort(d1, d2)
X.in +4n
Xstruct direct **d1;
Xstruct direct **d2;
X.in -4n
X.ft R
X.fi
X.SH DESCRIPTION
X.I Scandir
Xreads the directory
X.I name
Xand builds a NULL\-terminated array of pointers to the entries found
Xin that directory.
XThis array is put into the location pointed to by the
X.I list
Xparameter.
X.PP
XIf the
X.I selector
Xparameter is non\-NULL, it is taken to be a pointer to a function called
Xwith each entry, to determine whether or not it should be included in
Xthe returned list.
XIf the parameter is NULL, all entries are included.
X.PP
XAs an added feature, the entries can be sorted (with
X.IR qsort (3))
Xbefore the list is returned.
XIf the
X.I sorter
Xparameter is non\-NULL, it is passed to qsort to use as the comparison
Xfunction.
XThe
X.I alphasort
Xroutine is provided to sort the array alphabetically.
X.PP
XThe array pointed to by
X.I list
Xand the items it points to are all space obtained through
X.IR malloc (3),
Xand their storage can be reclaimed as shown in the example below.
X.SH "EXAMPLE"
XHere is a small
X.IR ls (1)\-like
Xprogram:
X.ne 50
X.RS
X.nf
X#include <stdio.h>
X#include <sys/types.h>
X#include <sys/stat.h>
X#include <sys/dir.h>
X
Xextern int alphasort();
X
Xstatic int
Xfilesonly(e)
X struct direct *e;
X{
X struct stat sb;
X
X return(stat(e->d_name, &sb) >= 0 && (sb.st_mode & S_IFMT) == S_IFREG);
X}
X
Xmain(ac, av)
X int ac;
X char *av[];
X{
X register int i;
X register int j;
X struct direct **list;
X
X if (ac != 2) {
X fprintf(stderr, "usage: %s dirname\n", av[0]);
X exit(1);
X }
X if (chdir(av[1]) < 0) {
X perror(av[1]);
X exit(1);
X }
X if ((i = scandir(".", &list, filesonly, alphasort)) < 0) {
X perror("Error reading directory");
X exit(1);
X }
X for (j = 0; j < i; j++)
X printf("%s\n", list[j]->d_name);
X for (j = 0; j < i; j++)
X free((char *)list[j]);
X free((char *)list);
X exit(0);
X}
X.fi
X.RE
X.SH "SEE ALSO"
Xdirectory(3), qsort(3)
X.SH DIAGNOSTICS
XReturns the number of entries in the ``list,'' or \-1 if the directory
Xcould not be opened or a memory allocation failed.
X.SH BUGS
XThe routine can be slightly wasteful of space.
END_OF_FILE
if test 2350 -ne `wc -c <'scandir.3'`; then
echo shar: \"'scandir.3'\" unpacked with wrong size!
fi
# end of 'scandir.3'
fi
if test -f 'scandir.c' -a "${1}" != "-c" ; then
echo shar: Will not clobber existing file \"'scandir.c'\"
else
echo shar: Extracting \"'scandir.c'\" \(1827 characters\)
sed "s/^X//" >'scandir.c' <<'END_OF_FILE'
X/*
X** SCANDIR
X** Scan a directory, collecting all (selected) items into a an array.
X*/
X
X#include <sys/types.h>
X#include <sys/dir.h>
X
X#ifdef RCSID
Xstatic char RCS[] = "$Header: scandir.c,v 1.1 87/12/29 21:35:56 rsalz Exp $";
X#endif /* RCSID */
X
X/* Initial guess at directory size. */
X#define INITIAL_SIZE 20
X
Xextern char *malloc();
Xextern char *realloc();
Xextern char *strcpy();
X
Xint
Xscandir(name, list, selector, sorter)
X char *name;
X struct direct ***list;
X int (*selector)();
X int (*sorter)();
X{
X register struct direct **names;
X register struct direct *entp;
X register DIR *dirp;
X register int i;
X register int size;
X
X /* Get initial list space and open directory. */
X size = INITIAL_SIZE;
X names = (struct direct **)malloc(size * sizeof names[0]);
X if (names == NULL)
X return -1;
X dirp = opendir(name);
X if (dirp == NULL)
X return -1;
X
X /* Read entries in the directory. */
X for (i = 0; entp = readdir(dirp); )
X if (selector == NULL || (*selector)(entp)) {
X /* User wants them all, or he wants this one. */
X if (++i >= size) {
X size <<= 1;
X names = (struct direct **)
X realloc((char *)names, size * sizeof names[0]);
X if (names == NULL) {
X closedir(dirp);
X return -1;
X }
X }
X
X /* Copy the entry. */
X names[i - 1] = (struct direct *)malloc(DIRSIZ(entp));
X if (names[i - 1] == NULL) {
X closedir(dirp);
X return -1;
X }
X names[i - 1]->d_ino = entp->d_ino;
X names[i - 1]->d_reclen = entp->d_reclen;
X names[i - 1]->d_namlen = entp->d_namlen;
X (void)strcpy(names[i - 1]->d_name, entp->d_name);
X }
X
X /* Close things off. */
X names[i] = NULL;
X *list = names;
X closedir(dirp);
X
X /* Sort? */
X if (i && sorter)
X qsort((char *)names, i, sizeof names[0], sorter);
X
X return i;
X}
END_OF_FILE
if test 1827 -ne `wc -c <'scandir.c'`; then
echo shar: \"'scandir.c'\" unpacked with wrong size!
fi
# end of 'scandir.c'
fi
echo shar: End of shell archive.
exit 0
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