Special variables

Special variables is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Special variables have a predefined meaning within the programming language. The task is to list the special variables used within the language.

AWK

There are two types of special variables within AWK: Control variables and Informative variables.

• dollarint variables - The dollarint special variables represent fields within a record
• ARGC - An informative variable that provides command line parameter information
• ARGV - An informative array that provides command line parameter information
• CONVFMT - A control variable that specifies the conversion format of numerical strings
• ENVIRON - An informative array that contains the environment strings
• FILENAME - An informative variable that provides the current input [filename]
• FNR - An informative variable that provides the record number within the current file
• FS - A control variable that specifies the input field separator
• NF - An informative variable that provides the number of fields within the current record
• NR - An informative variable that provides the total number of records processed
• OFMT - A control variable that specifies the output format of numerical values
• OFS - A control variable that specifies the output field separator
• ORS - A control variable that specifies the output record separator
• RLENGTH - An informative variable that provides the length of the currently matched substring
• RS - A control variable that specifies the input record separator
• RSTART - An informative variable that provides the start index of the currently matched substring
• SUBSEP - A control variable that specifies the subscript separator for multidimensional arrays

Icon and Unicon

Icon and Unicon have special variables known as keywords which are syntactically are preceded by an &. <lang Unicon>

1. &keyword # type returned(indicators) - brief description
2. indicators:
3. * - generates multiple values
4. = - modifiable
5. U - Unicon
6. G - Icon or Unicon with Graphics

&allocated # integer(*) - report memory use &ascii # cset - ASCII character set &clock # string - time of day &collections # integer(*) - garbage collection activity &column # integer(U) - source code column &cset # cset - universal character set &current # co-expression - current co-expression &date # string - today's date &dateline # string - time stamp &digits # cset - digit characters &dump # integer(=) - termination dump &e # real - natural log e &error # integer(=) - fail on error &errornumber # integer? - runtime error code &errortext # string? - runtime error message &errorvalue # any? - offending value &errout # file - standard error file &eventcode # integer(=U) - program execution event &eventsource # co-expression(=U) - source of program execution events &eventvalue # any(=U) - program execution value &fail # none - expression failure &features # string* - platform features &file # string - current source file &host # string - host machine name &input # file - standard input file &lcase # cset - lowercase letters &letters # cset - letters &level # integer - call depth &line # integer - current source line number &main # co-expression - main task &now # integer(U) - current time &null # null - null value &output # file - standard output file &phi # real - golden ratio &pos # integer(=) - string scanning position &progname # string(=) - program name &random # integer(=) - random number seed &regions # integer(*) - region sizes &source # co-expression - invoking co-expression &storage # integer(*) - memory in use &subject # string - string scanning subject &syserr # integer - halt on system error &time # integer(=) - elapsed time &trace # integer(=) - trace program &ucase # cset - upper case letters &version # string - version</lang>

J

special local variables

The names x y u v m n are used as parameters in explicit J definitions:

  y:  right argument
  x:  (optional) left argument
  u:  left argument to an adverb or conjunction
  v:  right argument to a conjunction
  m:  left noun argument to an adverb or conjunction (value error if verb provided)
  n:  right noun argument to a conjunction (value error if verb provided)

Note that the result of an adverb or conjunction that uses either x or y and one of these other names is always a verb. In this case, x and/or y represent arguments passed to the derived verb.

These names may be used as regular names, but that is bad practice except in the context of debugging or illustration.

special global variables

In J 602: Names in locale z are in the path for all locales, including the default locale (base) -- these provide "language features":

   names_z_''
ARGV           BINPATH        CR             CRLF           DEL            Debug          
EAV            EMPTY          FF             FIXFONT        FIXFONTWH      IF64           
IFCONSOLE      IFGTK          IFJ6           IFJAVA         IFJHS          IFUNIX         
IFWIN          IFWIN32        IFWINCE        IFWINE         IFWINNT        JVERSION       
LF             LF2            Note           PROFONT        SYSPPC         TAB            
UNAME          adverb         apply          assert         bind           boxopen        
boxxopen       break          bx             clear          coclass        cocreate       
cocurrent      codestroy      coerase        cofullname     coinsert       coname         
conames        conew          conjunction    conl           copath         coreset        
cutopen        datatype       def            define         do             drop           
dyad           each           edit           empty          erase          every          
exit           expand         fetch          inv            inverse        items          
jcwdpath       jhostpath      jpath          jpathsep       jsystemdefs    leaf           
list           load           loadd          loadp          mbopen         mbsave         
monad          nameclass      namelist       names          nc             nl             
noun           on             open           pick           require        rows           
script         scriptd        scripts        setbreak       sign           sminfo         
smoutput       sort           split          startupconsole startupide     table          
take           tmoutput       toCRLF         toHOST         toJ            tolower        
toupper        type           ucp            ucpcount       utf8           uucp           
verb           wcsize         wd             wdbox          wdcenter       wdclipread     
wdclipwrite    wde            wdfit          wdforms        wdget          wdhandler      
wdinfo         wdishandle     wdisparent     wdmove         wdpclose       wdqshow        
wdquery        wdreset        wdselect       wdstatus       winpathsep                    

Names in the locales j and jijs are available by explicity referencing those locales and are used to provide "system features" and "ide features":

   names_j_''
BOXES              BROWSER            CONFIRMCLOSE       DIRTREEX           DISPLAYLOAD        
EPSREADER          FORMAT             FORMSIZES          GetSystemMetrics   IFJIJX             
INPUTLOG           INPUTLOGFILE       LOADED             P2UPFONT           PATHJSEP           
PATHSEP            PDFREADER          PRINTERFONT        PRINTOPT           PUBLIC             
READONLY           SCRIPTS            SHOWSIP            SMPRINT            SM_CMONITORS       
SM_CXVIRTUALSCREEN SM_CYVIRTUALSCREEN SM_XVIRTUALSCREEN  SM_YVIRTUALSCREEN  STARTUP            
SYSTEMFOLDERS      TARGET             USERFOLDERS        WINPOS             XDIFF              
addfname           boxdraw            buildpublic        classwizard        cleantable         
config             cutnames           deb                debug              demos              
dirmatch           dltb               edit               editfind           editinputlog       
editinputprompt    exist              extijs             fexist             fif                
filenewform        fileprint          fileprintsetup     filex              fixWINPOS          
formedit           formeditrun        forms              fullname           getinputlog        
getpath            getscripts         gettarget          gettargetlocale    globaldefs         
gridwizard         help               htmlhelp           jpath              lab                
lastactive         loadp              open               openfiles          origin             
pacman             printfiles         prints             projectmanager     save               
saveuserfolders    scriptmake         scripts            wpreset            wpsave             
wpset                                                                                          
   names_jijs_''
EMPTY                      FIXFONTDEF                 FKEYS                      
FTYPES                     IFIOX                      IFMAX                      
IFREADONLY                 IFSAVED                    IFSHOW                     
JIJS                       JIJSMAC                    JRECENT                    
NEWUSER                    PPSCRIPT                   QFORMX                     
RECENT                     RECENTFILE                 RECENTLOC                  
RECENTMAX                  SCMP                       SMBLK                      
SMDESK                     SMHWNDP                    SMINIT                     
SMNAME                     SMPATH                     SMSEL                      
SMSIZE                     SMSTYLE                    SMTEXT                     
SMTORG                     aboutj                     boxfkeys                   
boxskeys                   checkreadonly              cleartemp                  
close                      closeijs                   closeijx                   
closewindows               comparesvn                 create                     
cutpara                    deb                        destroy                    
exitijs                    filecase                   fkeycase                   
fkeylist                   fkeyrun                    fkeyselect                 
fkeyselect1                flerase                    flexist                    
flopen                     flread                     flwrite                    
foldpara                   foldtext                   getSMSEL                   
getactsize                 getcascade                 getcascade1                
getcascades                getfile                    getformx                   
getline                    getsaveas                  getscrollpos               
getselection               getskey                    id2loc                     
id2name                    id2names                   id2type                    
ide_maximize               ide_minimize               ide_restore                
ifshiftkey                 iftempscript               info                       
intn                       jijs_aboutj_button         jijs_actrl_fkey            
jijs_bctrl_fkey            jijs_bctrlshift_fkey       jijs_cancel                
jijs_close                 jijs_close_button          jijs_dctrl_fkey            
jijs_default               jijs_demos_button          jijs_ectrl_fkey            
jijs_ectrlshift_fkey       jijs_editconfigure_button  jijs_editcopy_button       
jijs_editcut_button        jijs_editdirmatch_button   jijs_editexport_button     
jijs_editfif_button        jijs_editfind_button       jijs_editformedit_button   
jijs_editinputlog_button   jijs_editlint_button       jijs_editpaste_button      
jijs_editreadonly_button   jijs_editredo_button       jijs_editselectall_button  
jijs_editundo_button       jijs_f1_fkey               jijs_f1ctrl_fkey           
jijs_f1shift_fkey          jijs_fctrl_fkey            jijs_fctrlshift_fkey       
jijs_filecleartemp_button  jijs_fileexit_button       jijs_filenewclass_button   
jijs_filenewijs_button     jijs_fileopen_button       jijs_fileopensystem_button 
jijs_fileopenuser_button   jijs_fileprint_button      jijs_fileprintsetup_button 
jijs_filerecent_button     jijs_fkeys_button          jijs_forms_button          
jijs_gctrl_fkey            jijs_hctrl_fkey            jijs_helpconstants_button  
jijs_helpcontext_button    jijs_helpcontrols_button   jijs_helpdictionary_button 
jijs_helpforeigns_button   jijs_helpgeneral_button    jijs_helpgl2cmd_button     
jijs_helphelp_button       jijs_helpindex_button      jijs_helpphrases_button    
jijs_helpprimer_button     jijs_helprelease_button    jijs_helprelnotes_button   
jijs_helpuser_button       jijs_helpvocab_button      jijs_helpwdcmd_button      
jijs_helpwdover_button     jijs_ictrl_fkey            jijs_jctrl_fkey            
jijs_kctrl_fkey            jijs_kctrlshift_fkey       jijs_labadvance_button     
jijs_labauthor_button      jijs_labchapters_button    jijs_labs_button           
jijs_lctrl_fkey            jijs_lctrlshift_fkey       jijs_max_button            
jijs_mctrl_fkey            jijs_nctrl_fkey            jijs_nctrlshift_fkey       
jijs_octrl_fkey            jijs_pctrl_fkey            jijs_qctrl_fkey            
jijs_rctrl_fkey            jijs_rctrlshift_fkey       jijs_rundebug_button       
jijs_runfile_button        jijs_runfiled_button       jijs_runline_button        
jijs_runpacman_button      jijs_runprojman_button     jijs_runselection_button   
jijs_runwindow_button      jijs_runwindowd_button     jijs_save_button           
jijs_saveas_button         jijs_sctrl_fkey            jijs_sellower_button       
jijs_selminus_button       jijs_selplus_button        jijs_selplusline1_button   
jijs_selplusline2_button   jijs_selsort_button        jijs_seltoggle_button      
jijs_selupper_button       jijs_selwrap_button        jijs_tctrl_fkey            
jijs_tile_button           jijs_tileacross_button     jijs_tilecascade_button    
jijs_togglebox_button      jijs_wctrl_fkey            jijs_wctrlshift_fkey       
jrecent_cancel             jrecent_close              jrecent_enter              
jrecent_lb_button          jrecent_open_button        jrecent_run                
jrecent_run_button         jrecent_rund_button        jrecent_view_button        
lint                       marksavedid                name2id                    
new                        newijs                     newijx                     
nounrep                    openijs                    parentname                 
pathname                   pmovex                     qsmact                     
qsmall                     qsmallforms                qsmallijs                  
qsmlastijs                 qsmlastxs                  qsmout                     
qsmsize                    query                      quote                      
rdist                      readid                     readid16                   
readonlydefault            recent_open                recent_put                 
recent_read                recent_run                 recent_save                
resizefont                 restorefont                roundint                   
runcompare                 runexport                  runfile                    
runimmx0                   runimmx1                   runline                    
runselection               runwindow                  save                       
saveas                     saveopenwindows            scmp_cancel                
scmp_close                 scmp_close_button          scmp_current_button        
scmp_original_button       scmp_revert_button         scmp_run                   
scmp_show                  select_line                select_text                
set_fkeys                  set_skey1                  set_skeys                  
setfontall                 setpnall                   setreadonly                
sh                         smappend                   smclose                    
smfocus                    smfocusact                 smfocusout                 
smgetsel                   smmove                     smopen                     
smprompt                   smread                     smreplace                  
smsave                     smscroll                   smsel                      
smselact                   smselout                   smsetcmd                   
smsetsaved                 smsetselect                smwrite                    
sysmodifiers               tile                       tile2fit                   
tile2fit1                  tileacross                 tilecascade                
tileget                    todelim                    tofoldername               
togglebox                  togglereadonly             togglexs                   
tolist                     topara                     ucpboxdraw                 
unboxfkeys                 unboxskeys                 winmax                     

PureBasic

PureBasic has no 'special variables'. It does define constants that reflect compiler settings that can be tested and used as a part of compiling. All other non-explicitly declared values that vary during runtime are returned by functions.

Tcl

There are three major categories of special variables in Tcl: global variables special to the Tcl language, global variables set by Tcl-based interpreters, and local variables with special interpretations.

Language Globals

These variables are defined by the standard implementation of Tcl, and are present in all Tcl interpreters by default.

env

This global array is Tcl's interface to the process's environment variables.

errorCode

This global scalar holds a machine-readable description of the last error to occur. (Note that prior to Tcl 8.6, internally-generated exceptions often used NONE for this value.)

errorInfo

This global scalar holds a stack trace from the last error to occur.

tcl_library

This global scalar holds the location of Tcl's own internal library.

tcl_version, tcl_patchLevel

This global scalar holds the version of Tcl in use. From Tcl 8.5 onwards, these hold the same (detailed) value.

tcl_pkgPath

This global scalar holds a Tcl list of directories where Tcl looks for packages by default. This is used to initialize the auto_path global variable.

auto_path

This global scalar holds a Tcl list of directories where Tcl looks for packages (and auto-loaded scripts, though this facility is deprecated).

tcl_platform

This global array holds a description of the platform on which Tcl is executing.

tcl_precision

This global scalar holds the number of significant figures to use when converting a floating-point value to a string by default. From Tcl 8.5 onwards it should not be changed. (If you are thinking of using this, consider using the format command instead.)

tcl_rcFileName

This global scalar holds the name of a file to source when the interpreter starts in interactive mode.

tcl_rcRsrcName

This global scalar is only used on classic Mac OS (now deprecated); consult the documentation for more information.

tcl_traceCompile

If enabled at library configuration time, this global scalar allows tracing of the compilation of bytecode in the interpreter.

tcl_traceExec

If enabled at library configuration time, this global scalar allows tracing of the execution of bytecode in the interpreter.

tcl_wordchars, tcl_nonwordchars

These global scalars hold regular expression fragments that describe the current platform's interpretation of what is and isn't a word.

Interpreter Globals

These global variables are only features of the most common Tcl-based shells, tclsh and wish.

argc

This global scalar holds the number of arguments (after the script) passed to the Tcl interpreter.

argv

This global scalar holds a Tcl list of the arguments (after the script) passed to the Tcl interpreter.

argv0

This global scalar holds the name of the main script to execute that was passed to the Tcl interpreter, or the name of the interpreter itself in interactive mode.

tcl_interactive

This global scalar holds whether this interpreter is working in interactive mode (i.e., needs to print command prompts, run a REPL, etc.)

tcl_prompt1, tcl_prompt2

These global scalars allow customization of the prompt strings in interactive mode.

geometry

This global scalar holds the user-supplied preferred dimensions of the initial window. Only used by interpreters that load the Tk library.

Local Special Variables

This is a language feature of procedures.

args

This local variable holds the Tcl list of arguments supplied to the current procedure after all the other formal arguments have been satisfied. Note that it needs to be explicitly listed in the formal arguments and be last in the list of formal arguments to have this behavior.