file_is_executable

SFL
Version 2.11

`file_is_executable`

#include "sflfile.h"
Bool
file_is_executable (
    const char *filename)

Synopsis

Returns TRUE if the current process can execute the specified file. Directories are _not_ considered to be executable. Under DOS, Windows, appends ".com", ".exe", and ".bat" to the filename, in that order, to build a possible executable filename. If this fails, opens the file (if it exists) and examines the first few bytes of the file: if these are "#!", or '/'*! or "MZ" then the file is assumed to be executable. #! is a standard mechanism under Unix for indicating executable files. Note that process create() uses a compatible mechanism to launch the correct interpreter for such 'executable' scripts. NOTE: '/'*! is provided for REXX. [XXX] Under OS/2 appends ".exe" and ".cmd" to the filename, in that order, to be a possible executable filename. If this fails, it opens the file (if it exists) and examines the first few bytes of the file: if these are "#!" then the file is assumed to be executable. NOTE: REXX scripts MUST be in files named script.cmd in order to be found. BAT files are not considered, nor are COM files, since at present process_create does not support launching DOS processes. Under VMS, appends .exe and .com, in that order to build a possible executable filename. Does not search the PATH symbol; the filename must be specified with a path if necessary.

Source Code - (sflfile.c)

{
#if (defined (__UNIX__))
    ASSERT (filename);

    return ((file_mode (filename) & S_IEXEC) != 0
         && (file_mode (filename) & S_IFDIR) == 0);

#elif (defined (MSDOS_FILESYSTEM))
    Bool
        executable;                     /*  Return code                      */
    FILE
        *stream;                        /*  Opened file stream               */
    char
        input_char = 0,                 /*  First and second bytes of file   */
        *extension;                     /*  File extension, if any           */

    ASSERT (filename);

    /*  Find file extension; if not found, set extension to empty string     */
    extension = strrchr (filename, '.');
    if (extension == NULL
    ||  strchr (extension, '/')         /*  If last '.' is part of the path  */
    ||  strchr (extension, '\\'))       /*  then the filename has no ext.    */
        extension = "";

    /*  Windows: If extension is .exe/.com/.bat, the file is an executable   */
    /*  OS/2:    If the extension is .exe/.cmd, the file is an executable    */
#if (defined ( __OS2__))
    if (lexcmp (extension, ".exe") == 0
    ||  lexcmp (extension, ".cmd") == 0)
#else /* DOS, WINDOWS */
    if (lexcmp (extension, ".com") == 0
    ||  lexcmp (extension, ".exe") == 0
    ||  lexcmp (extension, ".bat") == 0)
#endif
        executable = file exists (filename);
    else
    /*  Windows: If the extension is empty, try .com, .exe, .bat             */
    /*  OS/2:    If the extension is empty, try .exe, .cmd                   */
    if (strnull (extension)
#if (defined( __OS2__))
    && (file exists (default extension (work_name, filename, "exe"))
    ||  file exists (default extension (work_name, filename, "cmd"))))
#else /* DOS, WINDOWS */
    && (file exists (default extension (work_name, filename, "com"))
    ||  file exists (default extension (work_name, filename, "exe"))
    ||  file exists (default extension (work_name, filename, "bat"))))
#endif
        executable = TRUE;              /*  Executable file found            */
    else
      {
        /*  Look for magic header at start of file                           */
        stream = file open (filename, 'r');
        if (stream)
          {
            input_char = fgetc (stream);
            executable = ((input_char == '#' && fgetc (stream) == '!')
#   if (defined (__WINDOWS__))
                       || (input_char == '/' && fgetc (stream) == '*'
                                             && fgetc (stream) == '!')
                       || (input_char == 'M' && fgetc (stream) == 'Z')
#   endif
                       );
            file close (stream);
          }
        else
            executable = FALSE;
      }
    return (executable);

#elif (defined (__VMS__))
    Bool
        executable;                     /*  Return code                      */
    char
        *extension;                     /*  File extension, if any           */

    ASSERT (filename);

    /*  Find file extension, if any                                          */
    extension = strrchr (filename, '.');
    if ((file_mode (filename) & S_IEXEC) != 0)
        executable = TRUE;
    else
    /*  If the extension is empty, try .exe and .com                         */
    if (!extension)
      {
        default extension (work_name, filename, "exe");
        if ((file_mode (work_name) & S_IEXEC) != 0)
            executable = TRUE;
        else
          {
            default extension (work_name, filename, "com");
            if ((file_mode (work_name) & S_IEXEC) != 0)
                executable = TRUE;
            else
                executable = FALSE;
          }
      }
    else
        executable = FALSE;

    return (executable);

#else
    return (FALSE);                     /*  Not supported on this system     */
#endif
}

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