File opening modes (r, w, a ...)
Lew Pitcher
lew.pitcher at digitalfreehold.ca
Thu Feb 22 20:42:59 EST 2018
jfong at ms4.hinet.net wrote:
> ast於 2018年2月22日星期四 UTC+8下午8時33分00秒寫道:
>> Hello
>>
>> I share a very valuable table I found on
>> StackOverflow about file opening modes
>>
>> If like me you always forget the details of
>> file opening mode, the following table provides
>> a good summary
>>
>> | r r+ w w+ a a+
>> ------------------|--------------------------
>> read | + + + +
>> write | + + + + +
>> write after seek | + + +
>> create | + + + +
>> truncate | + +
>> position at start | + + + +
>> position at end | + +
>
> What the "write after seek" means?
It /should/ mean that programs are permitted to seek to a point in the file,
and then write from that point on.
A write to a read mode ("r") file isn't permitted at all,
so neither is "write after seek" to a read mode file.
A write to an append mode ("a" and "a+") file always write to the end of the
file, effectively negating any seek.
HTH
--
Lew Pitcher
"In Skills, We Trust"
PGP public key available upon request
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