1.fp 5 CW 2.TH FTWALK 3 3.SH NAME 4\fBftwalk\fR \- file tree walker 5.SH SYNOPSIS 6.ta .75i 1.5i 2.25i 3i 3.75i 4.5i 5.25i 6i 7.PP 8.nf 9\f5 10#include <ftwalk.h> 11 12int ftwalk(char* path, int (*userf)(struct FTW* ftw), int options, 13 int (*comparf)(struct FTW* ftw1, struct FTW* ftw2)); 14 15 16int ftwflags(void); 17\fR 18.fi 19.SH DESCRIPTION 20.PP 21\fIFtwalk\fR traverses a directory hierarchy using depth-first search. 22Upon visiting each file or directory in the hierarchy, it calls 23the user function \fIuserf\fP to process that file or directory. 24On a directory object, \fIuserf\fR may be called twice, once in preorder 25and once in postorder. 26On a terminal object such as a file or an unreadable directory, 27\fIuserf\fP is called only once. 28Cycles due to hard links or symbolic links are detected 29to avoid infinite loops. 30.PP 31\fIPath\fR is the starting point of the search. 32It may be an absolute path name or a path name relative to 33the current directory. 34If \fIpath\fR is a null pointer or points to an empty string, it is treated 35as if it points to the current (dot) directory. 36.PP 37\fIOptions\fR consists of zero or more of the following bits: 38.IP 39FTW_CHILDREN: 40This implies preorder calls to \fIuserf\fR on directory objects. 41On such a call to \fIuserf\fR, 42the field \fIftw->link\fR (below) points to a link list of 43the children of the respective directory. 44Upon returning from \fIuserf\fP, 45if the field \fIftw->status\fR of any child object 46is set to FTW_SKIP (below), that child is pruned from the search. 47.IP 48FTW_DELAY: When \fBFTW_CHILDREN\fP is turned on, 49the fields \fIftw->statb\fP (\fIstruct stat\fP) of children objects 50remain undefined until these objects are visited. 51.IP 52FTW_DOT: Do not use \fIchdir\fR(2) during the traversal. 53Normally \fIchdir\fR is used so that 54the base name of the object about to be processed can be used 55in accessing its data. 56This can enhance \fIftwalk\fR efficiency but certain program effects 57such as core dumps may be generated in unexpected places 58or may not even be generated at all. 59Whenever \fIchdir\fR generates an error, if possible, 60the current directory is restored to the starting directory 61(see FTW_NAME and FTW_PATH). 62.IP 63FTW_MULTIPLE: The \fIpath\fP argument is treated as a \fIchar**\fP 64pointer to a null-terminated array of path names. 65All hierarchies rooted at these paths will be searched 66.IP 67FTW_POST: Calls to the user function are issued only in postorder. 68That is, \fIuserf\fP is called on a directory only after its descendants have 69been processed. 70The absence of this bit indicates that calls to the user functions 71are issued in preorder. That is, \fIuserf\fP is 72called on a directory before its descendants are processed. 73.IP 74FTW_PHYSICAL: Use \fIlstat\fR(2) instead of \fIstat\fR(2) to get 75file status and allow detection of symbolic links. 76In addition, if each component 77of the absolute path to the starting object has search permission, 78the absolute path is used for early detection of cycles. 79.IP 80FTW_META|FTW_PHYSICAL: Use \fIstat\fR(2) for top level file status and 81\fIlstat\fR(2) for all other files. 82Used to implement the POSIX 83.B \-H 84option for commands like 85.IR ls . 86.IP 87FTW_TWICE: Calls to the user function are issued in both preorder and postorder 88for directory objects. 89.IP 90FTW_USER: The first of 6 user defined option bits. 91These bits are ignored by \fIftwalk\fP. 92.PP 93\fIUserf\fR is a user supplied function that is 94called upon different visits of an object. 95If the return value of \fIuserf\fR is non-zero, 96\fIftwalk\fR returns immediately with the same value. 97The \fIuserf\fP prototype is: 98.PP 99.nf 100 int userf(struct FTW* ftw) 101.fi 102.PP 103\fBstruct FTW\fP contains at least the following elements: 104.PP 105.nf 106 struct FTW* link; /* link list of children */ 107 struct FTW* parent; /* parent object on the search path */ 108 union 109 { 110 long number; /* local number */ 111 void* pointer; /* local pointer */ 112 } local; /* user defined */ 113 struct stat statb; /* stat buffer of this object */ 114 char* path; /* full pathname */ 115 short pathlen; /* strlen(path) */ 116 unsigned short info; /* type of object */ 117 unsigned short status; /* status of object */ 118 short level; /* depth of object on the search path */ 119 short namelen; /* strlen(name) */ 120 char name[]; /* file name of object */ 121.fi 122.PP 123The \fIlink\fR field is normally NULL. 124If the option FTW_CHILDREN was turned on, 125it points to the start of the list of children 126of the directory being visited in preorder. 127Finally, if the directory being visited causes a cycle, 128\fIlink\fR points to the object on the search path that is 129identical to this directory. Note that if FTW_PHYSICAL was turned on, 130this may point to a directory that is an ancestor of the starting 131object. 132.PP 133The \fIparent\fR field points to the parent object 134on the search path. For convenience, a parent object is also supplied for 135the starting object. 136In this case, except for the \fIlocal\fR field which is initialized 137to 0 and the \fIlevel\fR field which contains a negative number, 138the rest of the structure may be undefined. 139.PP 140The \fIinfo\fR field indicates the type of the object 141being visited and the type of the visit. The types are: 142.IP 143FTW_D: A directory being visited in preorder, i.e., 144none of its children has been visited by the search. 145.IP 146FTW_DNX: A directory being visited in preorder that does not have 147search permission. 148.IP 149FTW_DP: A directory being visited in postorder, i.e., all of its 150descendants have been completely processed. 151.IP 152FTW_DC: A directory that causes cycles. This is a terminal object. 153.IP 154FTW_DNR: A directory that cannot be opened for reading. This is a terminal object. 155.IP 156FTW_F: An ordinary file. 157.IP 158FTW_SL: A symbolic link. 159Unless FTW_FOLLOW (below) is issued by the user function, 160this object is terminal. 161.IP 162FTW_NS: \fIStat\fR failed on this object. 163The stat buffer \fIstatb\fR is undefined. 164This object is terminal. 165.PP 166The \fIstatus\fR field of \fIstruct FTW\fR is used to communicate information 167between \fIftwalk\fR and \fIuserf\fR. On calls to \fIuserf\fR, it has one of 168two values: 169.IP 170FTW_NAME: The name of the object as defined in \fIftw->name\fR should be used for 171accessing its file information. This is because \fIchdir\fR(2) has been used 172to set the current directory to a suitable place (see FTW_CHDIR). 173.IP 174FTW_PATH: The argument \fIpath\fR of \fIuserf\fR should be used 175for accessing the file information of the object. 176.PP 177Upon returning, \fIuserf\fR may set the \fIstatus\fR field 178to one of the following values: 179.IP 180FTW_AGAIN: If this is a directory object being visited in postorder, 181it will be processed \fIagain\fR as if it had not been visited. 182.IP 183FTW_NOPOST: If this is a directory object being visited in preorder, 184the user function will not be called on its postorder visit. 185.IP 186FTW_SKIP: This object and its descendants are pruned from the search. 187.IP 188FTW_FOLLOW: If this object is a symbolic link, 189follow the link to its physical counterpart. 190.PP 191\fIComparf\fR, if not NULL, is a pointer to a function 192used to define a search ordering for children of a directory. 193If FTW_CHILDREN is turned on, the ordering of the children of 194a directory is done before the preorder call to \fIuserf\fR on that directory. 195Therefore, in that case, \fIftw->link\fR will point to the smallest child. 196.PP 197The \fIcomparf\fP prototype is: 198.PP 199.nf 200 int comparf(struct FTW* ftw1, struct FTW* ftw2) 201.fi 202.PP 203\fIComparf\fR should return a value <0, 0, or >0 to indicate whether 204\fIftw1\fR is considered smaller, equal, or larger than \fIftw2\fR. 205.PP 206\fIFtwalk\fR normally returns 0. 207On hard errors such as running out of memory, it returns -1. 208\fIFtwalk\fR may also return other values as discussed with respect 209to \fIuserf\fR. 210.PP 211\fIFtwflags\fR returns a combination of \fB0, FTW_META, FTW_PHYSICAL\fR 212according to the 213preferences specified by 214\fBastconf("PATH_RESOLVE",0,0)\fR: 215.TP 216.B logical 2170 218.TP 219.B metaphysical 220.B "FTW_META|FTW_PHYSICAL" 221.TP 222.B physical 223.B FTW_PHYSICAL 224.SH HISTORY 225\fIFtwalk\fR performs similar functions as that of 226the routine \fIftw\fR provided in System V. 227However, it is more general than \fIftw\fR 228and suitable for use as a base in implementing 229popular tools such as \fIls, find, tar, du,\fR and \fIrm\fR. 230\fIFtwalk\fR also handles symbolic links and hard links gracefully. 231.SH AUTHORS 232Phong Vo, Glenn Fowler, Dave Korn 233.SH SEE ALSO 234find(1), rm(1), du(1), ls(1), tar(1), stat(2), symlink(2), 235astfeature(3), ftw(3), pathcd(3) 236