usr_50.txt For Vim version 9.0. Last change: 2022 Jun 20 VIM USER MANUAL - by Bram Moolenaar Advanced Vim script writing 50.1 Exceptions 50.2 Function with variable number of arguments 50.3 Restoring the view Next chapter: usr_51.txt Create a plugin Previous chapter: usr_45.txt Select your language (local) Table of contents: usr_toc.txt ============================================================================== 50.1 Exceptions Let's start with an example: try read ~/templates/pascal.tmpl catch /E484:/ echo "Sorry, the Pascal template file cannot be found." endtry The read command will fail if the file does not exist. Instead of generating an error message, this code catches the error and gives the user a message with more information. For the commands in between try and endtry errors are turned into exceptions. An exception is a string. In the case of an error the string contains the error message. And every error message has a number. In this case, the error we catch contains "E484:". This number is guaranteed to stay the same (the text may change, e.g., it may be translated). Besides being able to give a nice error message, Vim will also continue executing commands after the :endtry. Otherwise, once an uncaught error is encountered, execution of the script/function/mapping will be aborted. When the read command causes another error, the pattern "E484:" will not match in it. Thus this exception will not be caught and result in the usual error message and execution is aborted. You might be tempted to do this: try read ~/templates/pascal.tmpl catch echo "Sorry, the Pascal template file cannot be found." endtry This means all errors are caught. But then you will not see an error that would indicate a completely different problem, such as "E21: Cannot make changes, 'modifiable' is off". Think twice before you catch any error! Another useful mechanism is the finally command: var tmp = tempname() try exe ":.,$write " .. tmp exe "!filter " .. tmp :.,$delete exe ":$read " .. tmp finally delete(tmp) endtry This filters the lines from the cursor until the end of the file through the "filter" command, which takes a file name argument. No matter if the filtering works, if something goes wrong in between try and finally or the user cancels the filtering by pressing CTRL-C, the delete(tmp) call is always executed. This makes sure you don't leave the temporary file behind. The finally does not catch the exception, the error will still abort further execution. More information about exception handling can be found in the reference manual: exception-handling. ============================================================================== 50.2 Function with variable number of arguments Vim enables you to define functions that have a variable number of arguments. The following command, for instance, defines a function that must have 1 argument (start) and can have up to 20 additional arguments: def Show(start: string, ...items: list<string>) The variable "items" will be a list in the function containing the extra arguments. You can use it like any list, for example: def Show(start: string, ...items: list<string>) echohl Title echo "start is " .. start echohl None for index in range(len(items)) echon $" Arg {index} is {items[index]}" endfor echo enddef You can call it like this: Show('Title', 'one', 'two', 'three') start is Title Arg 0 is one Arg 1 is two Arg 2 is three This uses the echohl command to specify the highlighting used for the following echo command. `echohl None` stops it again. The echon command works like echo, but doesn't output a line break. If you call it with one argument the "items" list will be empty. range(len(items)) returns a list with the indexes, what for loops over, we'll explain that further down. ============================================================================== 50.3 Restoring the view Sometimes you want to jump around, make a change and then go back to the same position and view. For example to change something in the file header. This can be done with two functions: var view = winsaveview() # Move around, make changes winrestview(view) ============================================================================== Next chapter: usr_51.txt Create a plugin Copyright: see manual-copyright vim:tw=78:ts=8:noet:ft=help:norl: