Updated May 2026; see History
IF <expr>
<statement(s) to execute if true>
ELSE
<statement(s) to execute if false>
ENDIF
IF, ELSE and ENDIF allow for the flow of control within a CMD or DO file based on various conditions that can be tested. IF takes an expression that evaluates to true or false, while ELSE and ENDIF take no arguments. See the example below and Command Files for more information.
Example
This DO file takes a filename argument, without extension. If the filename doesn't exist (with a BAS extension), it is created by copying from another file and then loaded into VUE. If no argument is supplied, or the file already exists, it prints an error message and exits. Note that the EXIT command exits entirely out of the CMD/DO file, regardless of the depth of IF/ENDIF nesting, unlike the ASB EXIT control statement.
IF "$0" = ""
:<This command needs a filename argument>
EXIT ; exit DO file
ELSE
IF LOOKUP("$0.BAS") = 0 ; if file does not exist
COPY $0.BAS=APPLIB:STDHDR.TXT
ELSE
:<$0.BAS already exists; command aborted>
EXIT ; exit DO file
ENDIF
ENDIF
VUE $0.BAS
History
2026 May, A-Shell 1786: Update IF.LIT (x.x.xxx) and ECHO.LIT (x.x.xxx) to support a new variable ($?) that equates to the exit status of the last module execution. For example:
RUN PROG1
ECHO PROG1 Exit Status: $?
IF $? <> 0
ECHO Error, cannot continue
GOTO ENDIT
ELSE
RUN PROG2
ENDIF
;ENDIT
Note that this variable is not recognized by DO.LIT.
