Special Command Line Characters

Commands entered at the IDL prompt are usually interpreted as IDL statements to be executed. Other interpretations include executive commands that control execution and compilation of programs, shell commands, and so on. Input to the IDL prompt is interpreted according to the first character of the line, as shown in the following table.

Note
The information in this section applies equally to IDL used in command-line mode or in the IDL Workbench.

Table 2-2: Interpretation of the First Character in an IDL Command
First Character	Action
.	Executive command. See About Executive Commands for details.
?	Help inquiry. For example, enter `?` on the Command Line to open the online help system. Enter `? .RUN` to open the Help system to the page that explains the .RUN command.
$	Send an operating system commands to a subprocess. Note - the SPAWN procedure is a more flexible alternative. It need not be used interactively and the standard output of the command can be saved in an IDL string array. See "SPAWN" (IDL Reference Guide) for details.
@	Batch file initiation.
↑ or ↓ key	Recall / edit previous commands.
Ctrl+D	In UNIX command-line mode, exits IDL, closes all files, and returns to operating system.
Ctrl+Z	In UNIX command-line mode, suspends IDL.
All others	IDL statement.

About Executive Commands

IDL executive commands compile programs, continue stopped programs, and start previously compiled programs. All of these commands begin with a period and must be entered in response to the IDL prompt. Commands can be entered in either uppercase or lowercase and can be abbreviated. Under UNIX, filenames are case sensitive; under Microsoft Windows, filenames can be specified in any case. See "Executive Commands" (IDL Quick Reference) for a descriptions of the available executive commands.

Note
Comments (prefaced by the semicolon character in IDL code) are not allowed within executive commands.

Executive commands are used to create $MAIN$ programs. See Creating $MAIN$ Programs for details.

Special Command Line Key Combination

When working at the command line, key combinations can be used to quickly edit a command. The line-editing abilities and the keys that activate them differ somewhat between the different operating systems. To access the history of commands entered at the command line, see Recalling Commands.

Note
The behavior can also differ within the same operating system, between the terminal window-based command line version of IDL and the Command Line view in the IDL Workbench.

The table below lists the edit functions and the corresponding keys in the terminal window (Command Line) and Workbench versions of IDL.

Table 2-3: Command Recall and Line Editing Keys
Function	IDL Command Line	IDL Workbench
Move cursor to start of line	Ctrl+A or Home	Ctrl+A or Home
Move cursor to end of line	Ctrl+E or End	Ctrl+A or Home
Move cursor left one character	Left arrow	Left arrow
Move cursor right one character	Right arrow	Right arrow
Move cursor left one word	Ctrl+B, (R13 on Sun Keyboard)	Ctrl+left arrow
Move cursor right one word	Ctrl+F, (R15 on Sun Keyboard)	Ctrl+right arrow
Delete from current to start of line	Ctrl+U	Ctrl+U
Delete from current to end of line	Ctrl+K	Ctrl+K
Delete current character	Ctrl+X or Ctrl+D	Ctrl+X or Delete
Delete previous character	Ctrl+H, or Backspace, or Delete	Backspace
Delete previous word	Ctrl+W, or Esc-Delete
Generate IDL keyboard interrupt	Ctrl+C	Ctrl+C (when a program is running)
Move back one line in recall buffer	Ctrl+N, Up arrow	Up arrow
Move forward one line in recall buffer	Down arrow	Down arrow
Redraw current line	Ctrl+R
Overstrike/Insert	Esc-I
EOF if current line is empty, else EOL	Ctrl+D
Search recall buffer for text	Available only in command-line mode. Enter ^ , then input search string at prompt.
Tab command matching	Available only for Windows. After entering a few characters, press Tab to cycle through all the matching commands in the command history.	After typing a few characters, press Tab to cycle through all the matching commands in the command history.
Insert the character at the current Executive Commands position	any character	any character
Parenthesis matching		Place cursor outside of parenthesis and IDL highlights the matching parenthesis.