The following is a list of some grub4dos internal variables and functions from a 2012 or later version of a chenall build of grub4dos (as included with the latest version of RMPrepUSB). Grub4dos variables have a maximum name length 8 characters and maximum value size of 512 characters. e.g.
StringsYou can get a substring of any variable like this: %variablename:~startpos,endpos% The endpos shows where it ends ( + position from the beginning, - position from the end) e.g set a=0123456789abcdefghijklmnopqrstuvwxyz echo %a:~0,3% displays 012 echo %a:~2,3% displays 234 echo %a:~-3,3% displays xyz echo %a:~3% displays 3456789abcdefghijklmnopqrstuvwxyz echo %a:~3,-2% displays 3456789abcdefghijklmnopqrstuvwx echo %a:~,-2% displays 0123456789abcdefghijklmnopqrstuvwx A header file which may help if you understand C code can be found here. Example - test string length of KEY is exactly 29 characters
Filename strings in batch filesIn a batch file, %0 is the full path of the batch file itself (if the batch file is in the root then no leading / is output), %~nx0 is the batch files filename + extension, %~n0 is just the filename and %~x0 is just the extension (e.g. .gb4). p is the path and d is the drive name.
If you pass more than one filename to a batch file, %1 will be the second parameter, %2 the third, etc. Internal named variablesgrub4dos has a few predefined variables - these can be used in a grub4dos command - e.g. echo %@date% or set d=%@date%
These are case sensitive:
@time - e.g. 15:29:11 @random - 0 to 32767 - e.g. set /a num1to10=%@random% / 3277 + 1 or set /a num1to10=%@random:~-1,1% + 1 @root - e.g. (hd0,0) @path - e.g. (bd)/BOOT/GRUB/ @retval - e.g. 1 ?_BOOT - e.g. (hd0,0) ?_WENV ?_UUID - set after uuid command - e.g. uuid (bd) ? - result of last command - e.g. cat --locate=string --number=1 /myfile && set offset=%?% && echo string found at %offset% prints 0x1de Fn callsYou can call an internal function like sprintf within a grub4dos menu or a grub4dos batch file. For example:
set a=aa
set b=bbb
call Fn.0 0 "stringa=%s stringb=%s" %a% %b%
this prints on the display
stringa=aa stringb=bbb
Here is a list of the Fn calls. I don't know all the details for all the parameters, but each parameter should be separated by a space.
Note that Fn. is case sensitive and must have a capital F and a lowercase n.
1 grub_putstr 2 putchar - e.g. call Fn.2 49 prints '1' 3 get_cmdline_obsolete 4 getxy The return value is ((X << 8) | Y). 5 gotoxy - e.g. call Fn.5 0 2 set cursor pos to beginning of line 11 6 cls 7 wee_skip_to was obsolete setcursor 8 nul_terminate 9 safe_parse_maxint_with_suffix 10 substring 11 grub_strstr - e.g. call Fn.11 0x6000 "$" 12 grub_strlen - e.g. call Fn.12 "freddy" && echo %@retval% - prints 6 13 grub_strtok - e.g. set /a p_hwid=0x40000 && call Fn.13 %p_hwid% "," or call Fn.13 0 "," || exit 14 grub_strncat 15 grub_strcmp compare two strings - e.g. call Fn.15 XXX XXX && echo %@retval% returns 0 (or -1 if no match) 16 grub_strcpy 17 reserved 18 19 getkey - gets a kbdchar 20 checkkey Check if any input character is available. 21 22 grub_memcmp 23 grub_memmove 24 grub_memset 25 26 grub_open - e.g. directly call grub_open file function it will put filesize at memory 0x8320 - this works well for non-compressed files too. call Fn.26 /myfile.gz && set /a filesize=*0x8320 27 grub_read 28 grub_close 29 30 31 32 devread 33 devwrite 34 next_partition 35 open_device 36 real_open_partition 37 set_device 38 39 40 41 parse_string 42 hexdump - e.g. call Fn.42 0x8000 0 3 - list 3 hex bytes at 0x8000 43 skip_to 44 builtin_cmd 45 get_datetime 46 find_command 47 48 49 get_mmap_entry 50 grub_malloc 51 grub_free51 52 list_partitions 53 realmode_run - executes a BIOS interrupt in real mode - e.g. see date.g4b batch file for example. 54 reserved for wee 55 reserved for wee 56 reserved for wee 57 reserved for wee 58 reserved for wee 59 reserved for wee 60 reserved for wee 61 dir - e.g. Fn.61 /dir/ 62 print_a_completion 63 print_completions 64 lba_to_chs 65 probe_bpb 66 probe_mbr 67 unicode_to_utf8 e.g. call Fn.67 *0x82d0 0x60000 3 cat (md)0x300+1,1 | set nt_ver=NT 68 rawread 69 rawwrite 70 setcursor e.g. call Fn.70 0 to disable cursor and splashimage 71 grub_tolower 72 grub_isspace 73 grub_sleep e.g. call Fn.73 3 to sleep for 3 secs 74 mem64 75 envi_cmd 76 strncmpx 77 rectangle 78 get_cmdline Internal Variable Locations held in memoryWhen grub4dos loads into memory, it will store certain internal, local values at defined places within memory. Sometimes it is useful to read or write to these locations.
For instance, the grub4dos version number is held at location 0x8278 in memory. So you can check what version the user is running by adding these lines to your grub4dos menu.lst file:
This checks the value of 0x8278 to ensure it is between 20120201 (the date that the grub4dos version was made) and -1 (which is the largest possible number). If this check fails then the message is displayed with a 3 second countdown and then the menu is exited.
Some variable locations + examples are given in the lists below: Address Length Description ========= ======== ============================================== 0000:8208 4 (DWORD) install_partition (the boot partition) 0000:8280 4 (DWORD) boot_drive (the boot drive) set /A BD=*0x8280&0xf0 if %BD%==0x80 echo We booted from a hard disk! 0000:8284 4 (DWORD) pxe_yip (your ip) 0000:8288 4 (DWORD) pxe_sip (server ip) 0000:828C 4 (DWORD) pxe_gip (gateway ip) 0000:8290 8 (QWORD) filesize (file size by last "cat --length=0") 0000:8298 4 (DWORD) saved_mem_upper (extended memory size in KB) 0000:829C 4 (DWORD) saved_partition (current root partition) 0000:82A0 4 (DWORD) saved_drive (current root drive) 0000:82A4 4 (DWORD) no_decompression (no auto gunzip) 0000:82A8 8 (QWORD) part_start (start sector of last partition) 0000:82B0 8 (QWORD) part_length (total sectors of last partition) 0x826C BSS start address (4 bytes) 0x8274 autonumber boot entries with a hyphen after the number - write 0x8274 0x2d01 0x8276 set /a CURDEF=*0x8276 & 0ff gets current menu item number as a variable CURDEF 0x8278 check version of grub4dos - e.g. checkrange 20120201:-1 read 0x8278 || pause --wait=3 Please use grub4dos-0.4.5c-2012-02-01 or later! && exit 1 0x8290 Length of file in bytes -e.g cat --length=0 /myfile.iso && set /a LEN=*0x8290 && echo Length of file is %LEN% bytes 0x8298 maximum free memory in KB starting at 1M and below 4G (memory may NOT be contiguous) # calculate sizes in MB of iso and available memory - set /a MEMSIZE=*0x8298&0xFFFFFFFF>>10 && cat --length=0 && /myfile.iso && set FSize=*0x8290>>20 && if %FSize%>=%MEMSIZE% && echo Need More memory! 0x82BC CPU type - iftitle [checkrange 0,1 read 0x82Bc] 32bit system 0x82D0 rd_base 0x82D8 rd_size 0x8320 to get the expanded length of a compresses .gz file - use: cat --length=1 /myfile.gz && set /a filesize=*0x8320 # Or directly call grub_open file function it will put filesize at memory 0x8320 - this works well for non-compressed files too. call Fn.26 /myfile.gz && set /a filesize=*0x8320 0x8328 filepos ptr
# get the UUID of a boot volume (note: do NOT use && to join these lines!)
^ anywhere inside a variable means do not translate to a variable - e.g. set a=%bb^bbb% returns a=%bbbbb% New operators (chenal grub4dos versions April 2013 and later)The && and || operators do not affect the environment until the whole line has been executed - e.g.
does not echo '1' because the environment is not updated until after the whole line has been executed. There are now three new operators: ;; - used to separate commands on the same line - e.g.
;& - as ;; but the next command is only executed if the result of the previous command was true, e.g.
;| - as ;; but next command is only executed if the previous command was falser |
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Grub4dos Internal variables and functions |