1 Config Language Specification
3 Michael Elizabeth Chastain, <mailto:mec@shout.net>
9 Config Language is not 'bash'.
11 This document describes Config Language, the Linux Kernel Configuration
12 Language. config.in and Config.in files are written in this language.
14 Although it looks, and usually acts, like a subset of the 'sh' language,
15 Config Language has a restricted syntax and different semantics.
17 Here is a basic guideline for Config Language programming: use only the
18 programming idioms that you see in existing Config.in files. People often
19 draw on their shell programming experience to invent idioms that look
20 reasonable to shell programmers, but silently fail in Config Language.
22 Config Language is not 'bash'.
28 Four different configuration programs read Config Language:
30 scripts/Configure make config, make oldconfig
31 scripts/Menuconfig make menuconfig
32 scripts/tkparse make xconfig
33 mconfig (in development)
35 'Configure' is a bash script which interprets Config.in files by sourcing
36 them. Some of the Config Language commands are native bash commands;
37 simple bash functions implement the rest of the commands.
39 'Menuconfig' is another bash script. It scans the input files with a
40 small awk script, builds a shell function for each menu, sources the
41 shell functions that it builds, and then executes the shell functions
42 in a user-driven order. Menuconfig uses 'lxdialog', a back-end utility
43 program, to perform actual screen output. 'lxdialog' is a C program
46 'scripts/tkparse' is a C program with an ad hoc parser which translates
47 a Config Language script to a huge TCL/TK program. 'make xconfig'
48 then hands this TCL/TK program to 'wish', which executes it.
50 'mconfig' is the next generation of Config Language interpreters. It is a
51 C program with a bison parser which translates a Config Language script
52 into an internal syntax tree and then hands the syntax tree to one of
53 several user-interface front ends.
55 This document describes the behaviour of all four interpreters, even though
56 mconfig has not been released at the time of writing.
62 A Config Language script is a list of statements. There are 21 simple
63 statements; an 'if' statement; menu blocks; and a 'source' statement.
65 A '\' at the end of a line marks a line continuation.
67 '#' usually introduces a comment, which continues to the end of the line.
68 Lines of the form '# ... is not set', however, are not comments. They
69 are semantically meaningful, and all four config interpreters implement
72 Newlines are significant. You may not substitute semicolons for newlines.
73 The 'if' statement does accept a semicolon in one position; you may use
74 a newline in that position instead.
76 Here are the basic grammar elements.
78 A /prompt/ is a single-quoted string or a double-quoted string.
79 If the word is double-quoted, it may not have any $ substitutions.
81 A /word/ is a single unquoted word, a single-quoted string, or a
82 double-quoted string. If the word is unquoted or double quoted,
83 then $-substition will be performed on the word.
85 A /symbol/ is a single unquoted word. A symbol must have a name of
86 the form CONFIG_*. scripts/mkdep.c relies on this convention in order
87 to generate dependencies on individual CONFIG_* symbols instead of
88 making one massive dependency on include/linux/autoconf.h.
90 A /dep/ is a dependency. Syntactically, it is a /word/. At run
91 time, a /dep/ must evaluate to "y", "m", "n", or "".
93 An /expr/ is a bash-like expression using the operators
94 '=', '!=', '-a', '-o', and '!'.
96 Here are all the statements:
100 mainmenu_name /prompt/
106 bool /prompt/ /symbol/
107 hex /prompt/ /symbol/ /word/
108 int /prompt/ /symbol/ /word/
109 string /prompt/ /symbol/ /word/
110 tristate /prompt/ /symbol/
114 define_bool /symbol/ /word/
115 define_hex /symbol/ /word/
116 define_int /symbol/ /word/
117 define_string /symbol/ /word/
118 define_tristate /symbol/ /word/
120 Dependent statements:
122 dep_bool /prompt/ /symbol/ /dep/ ...
123 dep_mbool /prompt/ /symbol/ /dep/ ...
124 dep_hex /prompt/ /symbol/ /word/ /dep/ ...
125 dep_int /prompt/ /symbol/ /word/ /dep/ ...
126 dep_string /prompt/ /symbol/ /word/ /dep/ ...
127 dep_tristate /prompt/ /symbol/ /dep/ ...
135 choice /prompt/ /word/ /word/
136 nchoice /prompt/ /symbol/ /prompt/ /symbol/ ...
155 mainmenu_option next_comment
167 === mainmenu_name /prompt/
169 This verb is a lot less important than it looks. It specifies the top-level
170 name of this Config Language file.
172 Configure: ignores this line
173 Menuconfig: ignores this line
174 Xconfig: uses /prompt/ for the label window.
175 mconfig: ignores this line (mconfig does a better job without it).
179 # arch/sparc/config.in
180 mainmenu_name "Linux/SPARC Kernel Configuration"
186 This verb displays its prompt to the user during the configuration process
187 and also echoes it to the output files during output. Note that the
188 prompt, like all prompts, is a quoted string with no dollar substitution.
190 The 'comment' verb is not a Config Language comment. It causes the
191 user interface to display text, and it causes output to appear in the
194 Configure: implemented
195 Menuconfig: implemented
201 # drivers/net/Config.in
202 comment 'CCP compressors for PPP are only built as modules.'
208 This verb displays the prompt to the user with no adornment whatsoever.
209 It does not echo the prompt to the output file. mconfig uses this verb
210 internally for its help facility.
212 Configure: not implemented
213 Menuconfig: not implemented
214 Xconfig: not implemented
219 # mconfig internal help text
220 text 'Here are all the mconfig command line options.'
224 === bool /prompt/ /symbol/
226 This verb displays /prompt/ to the user, accepts a value from the user,
227 and assigns that value to /symbol/. The legal input values are "n" and
230 Note that the bool verb does not have a default value. People keep
231 trying to write Config Language scripts with a default value for bool,
232 but *all* of the existing language interpreters discard additional values.
233 Feel free to submit a multi-interpreter patch to linux-kbuild if you
234 want to implement this as an enhancment.
236 Configure: implemented
237 Menuconfig: implemented
243 # arch/i386/config.in
244 bool 'Symmetric multi-processing support' CONFIG_SMP
248 === hex /prompt/ /symbol/ /word/
250 This verb displays /prompt/ to the user, accepts a value from the user,
251 and assigns that value to /symbol/. Any hexadecimal number is a legal
252 input value. /word/ is the default value.
254 The hex verb does not accept range parameters.
256 Configure: implemented
257 Menuconfig: implemented
263 # drivers/sound/Config.in
264 hex 'I/O base for SB Check from manual of the card' CONFIG_SB_BASE 220
268 === int /prompt/ /symbol/ /word/
270 This verb displays /prompt/ to the user, accepts a value from the user,
271 and assigns that value to /symbol/. /word/ is the default value.
272 Any decimal number is a legal input value.
274 The int verb does not accept range parameters.
276 Configure: implemented
277 Menuconfig: implemented
283 # drivers/char/Config.in
284 int 'Maximum number of Unix98 PTYs in use (0-2048)' \
285 CONFIG_UNIX98_PTY_COUNT 256
289 === string /prompt/ /symbol/ /word/
291 This verb displays /prompt/ to the user, accepts a value from the user,
292 and assigns that value to /symbol/. /word/ is the default value. Legal
293 input values are any ASCII string, except for the characters '"' and '\\'.
295 The default value is mandatory.
297 Configure: implemented
298 Menuconfig: implemented
304 # drivers/sound/Config.in
305 string ' Full pathname of DSPxxx.LD firmware file' \
306 CONFIG_PSS_BOOT_FILE /etc/sound/dsp001.ld
310 === tristate /prompt/ /symbol/
312 This verb displays /prompt/ to the user, accepts a value from the user,
313 and assigns that value to /symbol/. Legal values are "n", "m", or "y".
315 The value "m" stands for "module"; it indicates that /symbol/ should
316 be built as a kernel module. The value "m" is legal only if the symbol
317 CONFIG_MODULES currently has the value "y".
319 The tristate verb does not have a default value.
321 Configure: implemented
322 Menuconfig: implemented
329 tristate 'NFS filesystem support' CONFIG_NFS_FS
333 === define_bool /symbol/ /word/
335 This verb the value of /word/ to /symbol/. Legal values are "n" or "y".
337 For compatibility reasons, the value of "m" is also legal, because it
338 will be a while before define_tristate is implemented everywhere.
340 Configure: implemented
341 Menuconfig: implemented
347 # arch/alpha/config.in
348 if [ "$CONFIG_ALPHA_GENERIC" = "y" ]
350 define_bool CONFIG_PCI y
351 define_bool CONFIG_ALPHA_NEED_ROUNDING_EMULATION y
356 === define_hex /symbol/ /word/
358 This verb assigns the value of /word/ to /symbol/. Any hexadecimal
359 number is a legal value.
361 Configure: implemented
362 Menuconfig: implemented
368 # Not from the corpus
369 bool 'Specify custom serial port' CONFIG_SERIAL_PORT_CUSTOM
370 if [ "$CONFIG_SERIAL_PORT_CUSTOM" = "y" ]; then
371 hex 'Serial port number' CONFIG_SERIAL_PORT
373 define_hex CONFIG_SERIAL_PORT 0x3F8
378 === define_int /symbol/ /word/
380 This verb assigns /symbol/ the value /word/. Any decimal number is a
383 Configure: implemented
384 Menuconfig: implemented
390 # drivers/char/ftape/Config.in
391 define_int CONFIG_FT_ALPHA_CLOCK 0
395 === define_string /symbol/ /word/
397 This verb assigns the value of /word/ to /symbol/. Legal input values
398 are any ASCII string, except for the characters '"' and '\\'.
400 Configure: implemented
401 Menuconfig: implemented
407 # Not from the corpus
408 define_string CONFIG_VERSION "2.2.0"
412 === define_tristate /symbol/ /word/
414 This verb assigns the value of /word/ to /symbol/. Legal input values
415 are "n", "m", and "y".
417 As soon as this verb is implemented in all interpreters, please use it
418 instead of define_bool to define tristate values. This aids in static
421 Configure: implemented
422 Menuconfig: implemented
428 # drivers/video/Config.in
429 if [ "$CONFIG_FB_AMIGA" = "y" ]; then
430 define_tristate CONFIG_FBCON_AFB y
431 define_tristate CONFIG_FBCON_ILBM y
433 if [ "$CONFIG_FB_AMIGA" = "m" ]; then
434 define_tristate CONFIG_FBCON_AFB m
435 define_tristate CONFIG_FBCON_ILBM m
441 === dep_bool /prompt/ /symbol/ /dep/ ...
443 This verb evaluates all of the dependencies in the dependency list.
444 Any dependency which has a value of "y" does not restrict the input
445 range. Any dependency which has an empty value is ignored.
446 Any dependency which has a value of "n", or which has some other value,
447 (like "m") restricts the input range to "n". Quoting dependencies is not
448 allowed. Using dependencies with an empty value possible is not
449 recommended. See also dep_mbool below.
451 If the input range is restricted to the single choice "n", dep_bool
452 silently assigns "n" to /symbol/. If the input range has more than
453 one choice, dep_bool displays /prompt/ to the user, accepts a value
454 from the user, and assigns that value to /symbol/.
456 Configure: implemented
457 Menuconfig: implemented
463 # drivers/net/Config.in
464 dep_bool 'Aironet 4500/4800 PCI support 'CONFIG_AIRONET4500_PCI $CONFIG_PCI
467 - Xconfig does not write "# foo is not set" to .config (as well as
468 "#undef foo" to autoconf.h) if command is disabled by its dependencies.
471 === dep_mbool /prompt/ /symbol/ /dep/ ...
473 This verb evaluates all of the dependencies in the dependency list.
474 Any dependency which has a value of "y" or "m" does not restrict the
475 input range. Any dependency which has an empty value is ignored.
476 Any dependency which has a value of "n", or which has some other value,
477 restricts the input range to "n". Quoting dependencies is not allowed.
478 Using dependencies with an empty value possible is not recommended.
480 If the input range is restricted to the single choice "n", dep_bool
481 silently assigns "n" to /symbol/. If the input range has more than
482 one choice, dep_bool displays /prompt/ to the user, accepts a value
483 from the user, and assigns that value to /symbol/.
485 Notice that the only difference between dep_bool and dep_mbool
486 is in the way of treating the "m" value as a dependency.
488 Configure: implemented
489 Menuconfig: implemented
491 mconfig: not implemented
495 # Not from the corpus
496 dep_mbool 'Packet socket: mmapped IO' CONFIG_PACKET_MMAP $CONFIG_PACKET
499 - Xconfig does not write "# foo is not set" to .config (as well as
500 "#undef foo" to autoconf.h) if command is disabled by its dependencies.
503 === dep_hex /prompt/ /symbol/ /word/ /dep/ ...
504 === dep_int /prompt/ /symbol/ /word/ /dep/ ...
505 === dep_string /prompt/ /symbol/ /word/ /dep/ ...
507 I am still thinking about the semantics of these verbs.
509 Configure: not implemented
510 Menuconfig: not implemented
511 XConfig: not implemented
512 mconfig: not implemented
516 === dep_tristate /prompt/ /symbol/ /dep/ ...
518 This verb evaluates all of the dependencies in the dependency list.
519 Any dependency which has a value of "y" does not restrict the input range.
520 Any dependency which has a value of "m" restricts the input range to
521 "m" or "n". Any dependency which has an empty value is ignored.
522 Any dependency which has a value of "n", or which has some other value,
523 restricts the input range to "n". Quoting dependencies is not allowed.
524 Using dependencies with an empty value possible is not recommended.
526 If the input range is restricted to the single choice "n", dep_tristate
527 silently assigns "n" to /symbol/. If the input range has more than
528 one choice, dep_tristate displays /prompt/ to the user, accepts a value
529 from the user, and assigns that value to /symbol/.
531 Configure: implemented
532 Menuconfig: implemented
538 # drivers/char/Config.in
539 dep_tristate 'Parallel printer support' CONFIG_PRINTER $CONFIG_PARPORT
542 - Xconfig does not write "# foo is not set" to .config (as well as
543 "#undef foo" to autoconf.h) if command is disabled by its dependencies.
546 === unset /symbol/ ...
548 This verb assigns the value "" to /symbol/, but does not cause /symbol/
549 to appear in the output. The existence of this verb is a hack; it covers
550 up deeper problems with variable semantics in a random-execution language.
552 Configure: implemented
553 Menuconfig: implemented
554 Xconfig: implemented (with bugs)
559 # arch/mips/config.in
561 unset CONFIG_MIPS_JAZZ
562 unset CONFIG_VIDEO_G364
566 === choice /prompt/ /word/ /word/
568 This verb implements a choice list or "radio button list" selection.
569 It displays /prompt/ to the user, as well as a group of sub-prompts
570 which have corresponding symbols.
572 When the user selects a value, the choice verb sets the corresponding
573 symbol to "y" and sets all the other symbols in the choice list to "n".
575 The second argument is a single-quoted or double-quoted word that
576 describes a series of sub-prompts and symbol names. The interpreter
577 breaks up the word at white space boundaries into a list of sub-words.
578 The first sub-word is the first prompt; the second sub-word is the
579 first symbol. The third sub-word is the second prompt; the fourth
580 sub-word is the second symbol. And so on, for all the sub-words.
582 The third word is a literal word. Its value must be a unique abbreviation
583 for exactly one of the prompts. The symbol corresponding to this prompt
584 is the default enabled symbol.
586 Note that because of the syntax of the choice verb, the sub-prompts
587 may not have spaces in them.
589 Configure: implemented
590 Menuconfig: implemented
596 # arch/i386/config.in
597 choice ' PCI access mode' \
598 "BIOS CONFIG_PCI_GOBIOS \
599 Direct CONFIG_PCI_GODIRECT \
600 Any CONFIG_PCI_GOANY" Any
604 === nchoice /prompt/ /symbol/ /prompt/ /symbol/ ...
606 This verb has the same semantics as the choice verb, but with a sensible
609 The first /prompt/ is the master prompt for the entire choice list.
611 The first /symbol/ is the default symbol to enable (notice that this
612 is a symbol, not a unique prompt abbreviation).
614 The subsequent /prompt/ and /symbol/ pairs are the prompts and symbols
617 Configure: not implemented
618 Menuconfig: not implemented
619 XConfig: not implemented
624 === if [ /expr/ ] ; then
626 This is a conditional statement, with an optional 'else' clause. You may
627 substitute a newline for the semicolon if you choose.
629 /expr/ may contain the following atoms and operators. Note that, unlike
630 shell, you must use double quotes around every atom.
637 /atom/ = /atom/ true if atoms have identical value
638 /atom/ != /atom/ true if atoms have different value
641 /expr/ -o /expr/ true if either expression is true
642 /expr/ -a /expr/ true if both expressions are true
643 ! /expr/ true if expression is not true
645 Note that a naked /atom/ is not a valid /expr/. If you try to use it
649 if [ "$CONFIG_EXPERIMENTAL" ]; then
650 bool 'Bogus experimental feature' CONFIG_BOGUS
653 ... then you will be surprised, because CONFIG_EXPERIMENTAL never has a
654 value of the empty string! It is always "y" or "n", and both of these
655 are treated as true (non-empty) by the bash-based interpreters Configure
658 Configure: implemented
659 Menuconfig: implemented
660 XConfig: implemented, with bugs
663 Xconfig has some known bugs, and probably some unknown bugs too:
665 - literals with an empty "" value are not properly handled.
669 === mainmenu_option next_comment
671 This verb introduces a new menu. The next statement must have a comment
672 verb. The /prompt/ of that comment verb becomes the title of the menu.
673 (I have no idea why the original designer didn't create a 'menu ...' verb).
675 Statements outside the scope of any menu are in the implicit top menu.
676 The title of the top menu comes from a variety of sources, depending on
679 Configure: implemented
680 Menuconfig: implemented
688 This verb closes the scope of a menu.
690 Configure: implemented
691 Menuconfig: implemented
699 This verb interprets the literal /word/ as a filename, and interpolates
700 the contents of that file. The word must be a single unquoted literal
703 Some interpreters interpret this verb at run time; some interpreters
704 interpret it at parse time.
706 Inclusion is textual inclusion, like the C preprocessor #include facility.
707 The source verb does not imply a submenu or any kind of block nesting.
709 Configure: implemented (run time)
710 Menuconfig: implemented (parse time)
711 Xconfig: implemented (parse time)
712 mconfig: implemented (parse time)