Add function to get and change current directory (#5585)

* kernel: replace undocumented IsDir by IS_DIR

... which just returns a boolean. If we want a function that allows
detecting types of file system objects more generally, we can add
one in the future with a more appropriate name.

* kernel: add functions to get/change working dir

* Add ChangeDirectoryCurrent

doc/ref/files.xml

@@ -108,6 +108,7 @@ for more information how to do this.
 <#Include Label="Directory">
 <#Include Label="DirectoryTemporary">
 <#Include Label="DirectoryCurrent">
+<#Include Label="ChangeDirectoryCurrent">
 <#Include Label="DirectoriesLibrary">
 <#Include Label="DirectoriesSystemPrograms">
 <#Include Label="DirectoryContents">

lib/files.gd

@@ -497,7 +497,7 @@ DeclareGlobalFunction( "RemoveDirectoryRecursively" );
 InstallAtExit( function()
   local path;
   for path in GAPInfo.DirectoriesTemporary do
-      if IsDir(path) = 'D' then
+      if IS_DIR(path) then
           RemoveDirectoryRecursively(path);
       else
           PRINT_TO("*errout*", "Temporary directory already removed: ", path, "\n");
@@ -522,12 +522,37 @@ InstallAtExit( function()
 ##
 BIND_GLOBAL( "DirectoryCurrent", function()
     if IsBool( GAPInfo.DirectoryCurrent )  then
-        GAPInfo.DirectoryCurrent := Directory("./");
+        GAPInfo.DirectoryCurrent := Directory(GAP_getcwd());
     fi;
     return GAPInfo.DirectoryCurrent;
 end );
 
 
+#############################################################################
+##
+#F  ChangeDirectoryCurrent()  . . . . . . . . . . .  change current directory
+##
+##  <#GAPDoc Label="ChangeDirectoryCurrent">
+##  <ManSection>
+##  <Func Name="ChangeDirectoryCurrent" Arg='path'/>
+##
+##  <Description>
+##  Changes the current directory. Returns <K>true</K> on success and
+##  <K>fail</K> on failure.
+##  </Description>
+##  </ManSection>
+##  <#/GAPDoc>
+##
+BIND_GLOBAL( "ChangeDirectoryCurrent", function( path )
+    if GAP_chdir(path) = true then
+        GAPInfo.DirectoryCurrent := Directory(GAP_getcwd());
+        return true;
+    else
+        return fail;
+    fi;
+end );
+
+
 #############################################################################
 ##
 #F  CrcFile( <filename> )  . . . . . . . . . . . . . . . .  create crc value

lib/files.gi

@@ -369,7 +369,7 @@ InstallGlobalFunction(RemoveDirectoryRecursively,
   function(dirname)
     # dirname must be a string
     local Dowork;
-    if not(IsDir(dirname) = 'D') then
+    if not IS_DIR(dirname) then
         Error("dirname must be a directory");
         return fail;
     fi;
@@ -383,13 +383,12 @@ InstallGlobalFunction(RemoveDirectoryRecursively,
     fi;
     Dowork := function(pathname)
       # pathname does not end in a / and is known to be a proper directory
-      local c,f,fullname,what;
+      local c,f,fullname;
       c := DirectoryContents(pathname);
       for f in c do
           if f <> "." and f <> ".." then
               fullname := Concatenation(pathname,"/",f);
-              what := IsDir(fullname);
-              if what = 'D' then
+              if IS_DIR(fullname) then
                   Dowork(fullname);
               else
                   RemoveFile(fullname);

src/streams.c

@@ -1037,17 +1037,48 @@ static Obj FuncRemoveDir(Obj self, Obj filename)
 
 /****************************************************************************
 **
-*F  FuncIsDir( <self>, <name> )  . . . . . check whether something is a dir
+*F  FuncIS_DIR( <self>, <path> )  . . . . . check whether something is a dir
 */
-static Obj FuncIsDir(Obj self, Obj filename)
+static Obj FuncIS_DIR(Obj self, Obj path)
 {
-    RequireStringRep(SELF_NAME, filename);
+    RequireStringRep(SELF_NAME, path);
 
     // call the system dependent function
-    return SyIsDir( CONST_CSTR_STRING(filename) );
+    return SyFileType(CONST_CSTR_STRING(path)) == 'D' ? True : False;
+}
+
+/****************************************************************************
+**
+*F  FuncGAP_getcwd( <self> ) . . . . . . . . . get working directory pathname
+*/
+static Obj FuncGAP_getcwd(Obj self)
+{
+    char * res;
+    char   buf[GAP_PATH_MAX];
+
+    res = getcwd(buf, sizeof(buf));
+    if (res == NULL) {
+        SySetErrorNo();
+        return Fail;
+    }
+    return MakeImmString(buf);
 }
 
+/****************************************************************************
+**
+*F  FuncGAP_chdir( <self>, <path> ) . . . .  change current working directory
+*/
+static Obj FuncGAP_chdir(Obj self, Obj path)
+{
+    RequireStringRep(SELF_NAME, path);
 
+    int res = chdir(CONST_CSTR_STRING(path));
+    if (res < 0) {
+        SySetErrorNo();
+        return Fail;
+    }
+    return True;
+}
 
 
 /****************************************************************************
@@ -1682,7 +1713,9 @@ static StructGVarFunc GVarFuncs[] = {
     GVAR_FUNC_1ARGS(RemoveFile, filename),
     GVAR_FUNC_1ARGS(CreateDir, filename),
     GVAR_FUNC_1ARGS(RemoveDir, filename),
-    GVAR_FUNC_1ARGS(IsDir, filename),
+    GVAR_FUNC_1ARGS(IS_DIR, path),
+    GVAR_FUNC_0ARGS(GAP_getcwd),
+    GVAR_FUNC_1ARGS(GAP_chdir, path),
     GVAR_FUNC_0ARGS(LastSystemError),
     GVAR_FUNC_1ARGS(IsExistingFile, filename),
     GVAR_FUNC_1ARGS(IsReadableFile, filename),

src/sysfiles.c

@@ -2949,38 +2949,51 @@ Int SyRmdir ( const Char * name )
 
 /****************************************************************************
 **
-*F  SyIsDir( <name> )  . . . . . . . . . . . . .  test if something is a dir
-**
-**  Returns 'F' for a regular file, 'L' for a symbolic link and 'D'
-**  for a real directory, 'C' for a character device, 'B' for a block
-**  device 'P' for a FIFO (named pipe) and 'S' for a socket.
+*F  SyFileType( <path> )
+**
+**  Return a character describing the filesystem object with the given path:
+**  - 'F' for a regular file
+**  - 'L' for a symbolic link
+**  - 'D' for a directory
+**  - 'C' for a character device
+**  - 'B' for a block device
+**  - 'P' for a FIFO (named pipe)
+**  - 'S' for a socket
+**  - `\0` if there was en error (e.g. invalid path, unknown type, etc.)
 */
-Obj SyIsDir ( const Char * name )
+char SyFileType(const Char * path)
 {
-  Int res;
-  struct stat ourlstatbuf;
+    int         res;
+    struct stat ourlstatbuf;
 
-  res = lstat(name,&ourlstatbuf);
-  if (res < 0) {
-    SySetErrorNo();
-    return Fail;
-  }
-  if      (S_ISREG(ourlstatbuf.st_mode)) return ObjsChar['F'];
-  else if (S_ISDIR(ourlstatbuf.st_mode)) return ObjsChar['D'];
-  else if (S_ISLNK(ourlstatbuf.st_mode)) return ObjsChar['L'];
+    res = lstat(path, &ourlstatbuf);
+    if (res < 0) {
+        SySetErrorNo();
+        return 0;
+    }
+    if (S_ISREG(ourlstatbuf.st_mode))
+        return 'F';
+    if (S_ISDIR(ourlstatbuf.st_mode))
+        return 'D';
+    if (S_ISLNK(ourlstatbuf.st_mode))
+        return 'L';
 #ifdef S_ISCHR
-  else if (S_ISCHR(ourlstatbuf.st_mode)) return ObjsChar['C'];
+    if (S_ISCHR(ourlstatbuf.st_mode))
+        return 'C';
 #endif
 #ifdef S_ISBLK
-  else if (S_ISBLK(ourlstatbuf.st_mode)) return ObjsChar['B'];
+    if (S_ISBLK(ourlstatbuf.st_mode))
+        return 'B';
 #endif
 #ifdef S_ISFIFO
-  else if (S_ISFIFO(ourlstatbuf.st_mode)) return ObjsChar['P'];
+    if (S_ISFIFO(ourlstatbuf.st_mode))
+        return 'P';
 #endif
 #ifdef S_ISSOCK
-  else if (S_ISSOCK(ourlstatbuf.st_mode)) return ObjsChar['S'];
+    if (S_ISSOCK(ourlstatbuf.st_mode))
+        return 'S';
 #endif
-  else return ObjsChar['?'];
+    return 0;
 }
 
 

src/sysfiles.h

@@ -411,13 +411,19 @@ Int SyRmdir(const Char * name);
 
 /****************************************************************************
 **
-*F  SyIsDir( <name> )  . . . . . . . . . . . . .  test if something is a dir
-**
-**  Returns 'F' for a regular file, 'L' for a symbolic link and 'D'
-**  for a real directory, 'C' for a character device, 'B' for a block
-**  device 'P' for a FIFO (named pipe) and 'S' for a socket.
-*/
-Obj SyIsDir(const Char * name);
+*F  SyFileType( <path> )
+**
+**  Return a character describing the filesystem object with the given path:
+**  - 'F' for a regular file
+**  - 'L' for a symbolic link
+**  - 'D' for a directory
+**  - 'C' for a character device
+**  - 'B' for a block device
+**  - 'P' for a FIFO (named pipe)
+**  - 'S' for a socket
+**  - `\0` if there was en error (e.g. invalid path, unknown type, etc.)
+*/
+char SyFileType(const Char * path);
 
 
 /****************************************************************************

tst/testinstall/kernel/streams.tst

@@ -169,32 +169,32 @@ gap> CreateDir(fail);
 Error, CreateDir: <filename> must be a string (not the value 'fail')
 gap> RemoveDir(fail);
 Error, RemoveDir: <filename> must be a string (not the value 'fail')
-gap> IsDir(fail);
-Error, IsDir: <filename> must be a string (not the value 'fail')
+gap> IS_DIR(fail);
+Error, IS_DIR: <path> must be a string (not the value 'fail')
 
 #
 gap> tmpdir := MakeImmutable(TmpDirectory());;
 gap> subdir := MakeImmutable(Concatenation(tmpdir, "/subdir"));;
 gap> CreateDir(subdir);
 true
-gap> IsDir(subdir);
-'D'
+gap> IS_DIR(subdir);
+true
 gap> RemoveDir(subdir);
 true
-gap> IsDir(subdir);
-fail
+gap> IS_DIR(subdir);
+false
 gap> CreateDir(subdir);
 true
 gap> FileString(Concatenation(subdir, "/file"), "data");
 4
-gap> IsDir(subdir);
-'D'
+gap> IS_DIR(subdir);
+true
 gap> RemoveDirectoryRecursively(tmpdir);
 true
-gap> IsDir(subdir);
-fail
-gap> IsDir(tmpdir);
-fail
+gap> IS_DIR(subdir);
+false
+gap> IS_DIR(tmpdir);
+false
 
 #
 gap> IsExistingFile(fail);