files/file_perms.c

+/* file_perms.c
+
+   Return a string representation of a file permissions mask.
+*/
 #include <sys/stat.h>
 #include <stdio.h>
 #include "file_perms.h"                 /* Interface for this implementation */
 
 #define STR_SIZE sizeof("rwxrwxrwx")
 
 char *          /* Return ls(1)-style string for file permissions mask */
 filePermStr(mode_t perm, int flags)
 {
     static char str[STR_SIZE];
 
+    /* If FP_SPECIAL was specified, we emulate the trickery of ls(1) in
+       returning set-user-ID, set-group-ID, and sticky bit information in
+       the user/group/other execute fields. This is made more complex by
+       the fact that the case of the character displayed for this bits
+       depends on whether the corresponding execute bit is on or off. */
+
     snprintf(str, STR_SIZE, "%c%c%c%c%c%c%c%c%c",
         (perm & S_IRUSR) ? 'r' : '-', (perm & S_IWUSR) ? 'w' : '-',
         (perm & S_IXUSR) ?
             (((perm & S_ISUID) && (flags & FP_SPECIAL)) ? 's' : 'x') :
             (((perm & S_ISUID) && (flags & FP_SPECIAL)) ? 'S' : '-'),
         (perm & S_IRGRP) ? 'r' : '-', (perm & S_IWGRP) ? 'w' : '-',
         (perm & S_IXGRP) ?
             (((perm & S_ISGID) && (flags & FP_SPECIAL)) ? 's' : 'x') :
             (((perm & S_ISGID) && (flags & FP_SPECIAL)) ? 'S' : '-'),
         (perm & S_IROTH) ? 'r' : '-', (perm & S_IWOTH) ? 'w' : '-',
         (perm & S_IXOTH) ?
             (((perm & S_ISVTX) && (flags & FP_SPECIAL)) ? 't' : 'x') :
             (((perm & S_ISVTX) && (flags & FP_SPECIAL)) ? 'T' : '-'));
 
     return str;
 }