Re: Insert lines at begin of file with writefile

2017-05-30 14:21 GMT+03:00 Ni Va <nivaemail@gmail.com>:
> Le mardi 30 mai 2017 13:03:38 UTC+2, ZyX a écrit :
>> 2017-05-30 11:21 GMT+03:00 Ni Va <nivaemail@gmail.com>:
>> > Hi,
>> >
>> >
>> > Is that a way to tell writefile() func to append lines at the beginning of file?
>>
>> Just read the whole file, prepend and then write the whole file. In
>> any case I do not know a way to actually prepend bytes to the file: if
>> you seek to the end of file (or open it in append mode) and start
>> writing to it you get appending. If you seek to the start and start
>> writing you will just overwrite first bytes. So programming languages
>> do not have "prepending" abstraction because it is not supported by
>> the OS and thus is going to either cost very much or have problems
>> like loosing data on crashes.
>>
>> >
>> > Thank you
>> > Niva
>> >
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>
> Do you think readfile writefile would be faster than that :
>
> let begin = [$vimruntime."/gvim.exe", "-c", "edit ".makefile, "-c",
> \"call append(0, ".string(lines2Append).")", "-c", "wq"]
> call x.add_cmd(begin) " ==>>>> Launch cmd as job

With readfile+writefile you load a file into memory and write there.
With gvim you are forking, loading gvim.exe and a big bunch of
libraries needed for GUI, loading a file into memory (though buffer
structure should be a bit more efficient then a list from `readfile()`
AFAIK), loading a big bunch of plugins (do not do such things without
`-u NONE -i NONE`), loading GUI (use `--cmd` for such things, not
`-c`). Which is faster? Actually may be your variant if you do not
need to wait for gvim to finish prepending because time would be
limited to only forking. readfile()+writefile() if you do need to
wait.

>
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