Getting the pwd -L behavior right is fiddly.

1 files changed, 31 insertions, 13 deletions

diff --git a/toys/posix/pwd.c b/toys/posix/pwd.c
index 5c543e87..32035924 100644
--- a/toys/posix/pwd.c
+++ b/toys/posix/pwd.c
@@ -2,9 +2,9 @@
  *
  * Copyright 2006 Rob Landley <rob@landley.net>
  *
- * See http://opengroup.org/onlinepubs/9699919799/utilities/echo.html
+ * See http://opengroup.org/onlinepubs/9699919799/utilities/pwd.html
 
-USE_PWD(NEWTOY(pwd, ">0LP[!LP]", TOYFLAG_BIN))
+USE_PWD(NEWTOY(pwd, ">0LP[-LP]", TOYFLAG_BIN))
 
 config PWD
   bool "pwd"
@@ -12,12 +12,10 @@ config PWD
   help
     usage: pwd [-L|-P]
 
-    The print working directory command prints the current directory.
+    Print working (current) directory.
 
-    -P  Avoid all symlinks
-    -L  Use the value of the environment variable "PWD" if valid
-
-    The option "-L" is implied by default.
+    -L  Use shell's path from $PWD (when applicable)
+    -P  Print cannonical absolute path
 */
 
 #define FOR_pwd
@@ -25,12 +23,32 @@ config PWD
 
 void pwd_main(void)
 {
-  char *pwd = xgetcwd(), *env_pwd;
-  struct stat st[2];
+  char *s, *pwd = getcwd(0, 0), *PWD;
+
+  // Only use $PWD if it's an absolute path alias for cwd with no "." or ".."
+  if (!(toys.optflags & FLAG_P) && (s = PWD = getenv("PWD"))) {
+    struct stat st1, st2;
+
+    while (*s == '/') {
+      if (*(++s) == '.') {
+        if (s[1] == '/' || !s[1]) break;
+        if (s[1] == '.' && (s[2] == '/' || !s[2])) break;
+      }
+      while (*s && *s != '/') s++;
+    }
+    if (!*s && s != PWD) s = PWD;
+    else s = NULL;
+
+    // If current directory exists, make sure it matches.
+    if (s && pwd)
+        if (stat(pwd, &st1) || stat(PWD, &st2) || st1.st_ino != st2.st_ino ||
+            st1.st_dev != st2.st_dev) s = NULL;
+  } else s = NULL;
+
+  // If -L didn't give us a valid path, use cwd.
+  if (!s && !(s = pwd)) perror_exit("xgetcwd");
+
+  xprintf("%s\n", s);
 
-  if (!(toys.optflags & FLAG_P) && (env_pwd = getenv("PWD")) &&
-    !stat(pwd, &st[0]) && !stat(env_pwd, &st[1]) &&
-    (st[0].st_ino == st[1].st_ino)) xprintf("%s\n", env_pwd);
-  else xprintf("%s\n", pwd);
   if (CFG_TOYBOX_FREE) free(pwd);
 }