Prefer $HOME when looking up the current user's home directory.

When we need to identify the home directory on non-Windows, first
consult getenv("HOME").  If that's empty or unset, fall back
on our previous method of checking the <pwd.h> database.

Preferring $HOME allows the user to intentionally point at some
other directory, and it seems to be in line with the behavior of
most other utilities.  However, we shouldn't rely on it completely,
as $HOME is likely to be unset when running as a daemon.

Anders Kaseorg

Discussion: https://postgr.es/m/1634252654444.90107@mit.edu

src/bin/psql/command.c

@@ -558,19 +558,25 @@ exec_command_cd(PsqlScanState scan_state, bool active_branch, const char *cmd)
 		else
 		{
 #ifndef WIN32
-			struct passwd *pw;
-			uid_t		user_id = geteuid();
-
-			errno = 0;			/* clear errno before call */
-			pw = getpwuid(user_id);
-			if (!pw)
+			/* This should match get_home_path() */
+			dir = getenv("HOME");
+			if (dir == NULL || dir[0] == '\0')
 			{
-				pg_log_error("could not get home directory for user ID %ld: %s",
-							 (long) user_id,
-							 errno ? strerror(errno) : _("user does not exist"));
-				exit(EXIT_FAILURE);
+				uid_t		user_id = geteuid();
+				struct passwd *pw;
+
+				errno = 0;		/* clear errno before call */
+				pw = getpwuid(user_id);
+				if (pw)
+					dir = pw->pw_dir;
+				else
+				{
+					pg_log_error("could not get home directory for user ID %ld: %s",
+								 (long) user_id,
+								 errno ? strerror(errno) : _("user does not exist"));
+					success = false;
+				}
 			}
-			dir = pw->pw_dir;
 #else							/* WIN32 */
 
 			/*
@@ -581,7 +587,8 @@ exec_command_cd(PsqlScanState scan_state, bool active_branch, const char *cmd)
 #endif							/* WIN32 */
 		}
 
-		if (chdir(dir) == -1)
+		if (success &&
+			chdir(dir) < 0)
 		{
 			pg_log_error("\\%s: could not change directory to \"%s\": %m",
 						 cmd, dir);

src/interfaces/libpq/fe-connect.c

@@ -7267,14 +7267,21 @@ bool
 pqGetHomeDirectory(char *buf, int bufsize)
 {
 #ifndef WIN32
-	char		pwdbuf[BUFSIZ];
-	struct passwd pwdstr;
-	struct passwd *pwd = NULL;
+	const char *home;
 
-	(void) pqGetpwuid(geteuid(), &pwdstr, pwdbuf, sizeof(pwdbuf), &pwd);
-	if (pwd == NULL)
-		return false;
-	strlcpy(buf, pwd->pw_dir, bufsize);
+	home = getenv("HOME");
+	if (home == NULL || home[0] == '\0')
+	{
+		char		pwdbuf[BUFSIZ];
+		struct passwd pwdstr;
+		struct passwd *pwd = NULL;
+
+		(void) pqGetpwuid(geteuid(), &pwdstr, pwdbuf, sizeof(pwdbuf), &pwd);
+		if (pwd == NULL)
+			return false;
+		home = pwd->pw_dir;
+	}
+	strlcpy(buf, home, bufsize);
 	return true;
 #else
 	char		tmppath[MAX_PATH];

src/port/path.c

@@ -807,14 +807,25 @@ bool
 get_home_path(char *ret_path)
 {
 #ifndef WIN32
-	char		pwdbuf[BUFSIZ];
-	struct passwd pwdstr;
-	struct passwd *pwd = NULL;
+	/*
+	 * We first consult $HOME.  If that's unset, try to get the info from
+	 * <pwd.h>.
+	 */
+	const char *home;
 
-	(void) pqGetpwuid(geteuid(), &pwdstr, pwdbuf, sizeof(pwdbuf), &pwd);
-	if (pwd == NULL)
-		return false;
-	strlcpy(ret_path, pwd->pw_dir, MAXPGPATH);
+	home = getenv("HOME");
+	if (home == NULL || home[0] == '\0')
+	{
+		char		pwdbuf[BUFSIZ];
+		struct passwd pwdstr;
+		struct passwd *pwd = NULL;
+
+		(void) pqGetpwuid(geteuid(), &pwdstr, pwdbuf, sizeof(pwdbuf), &pwd);
+		if (pwd == NULL)
+			return false;
+		home = pwd->pw_dir;
+	}
+	strlcpy(ret_path, home, MAXPGPATH);
 	return true;
 #else
 	char	   *tmppath;