/g/ - syscall of the day: (f)truncate - Technology

Anonymous

syscall of the day: (f)truncat(...) 03/05/26(Thu)10:20:54 No.108301681

File: 1770469383193867.png (459 KB, 720x480)

syscall of the day: (f)truncate Anonymous 03/05/26(Thu)10:20:54 No.108301681 Archived

previous: >>108292753
#define __NR_truncate            76
#define __NR_ftruncate            77
https://man7.org/linux/man-pages/man2/truncate.2.html

tl;dr:
set a file to a specific length

that's all you're getting from me today because i'm in a rush
only other thing i will add is it's pretty bizarre (from a naming perspective) that you can "truncate" a file to a larger size

relevant resources:
man man
man syscalls
https://man7.org/linux/man-pages/
https://linux.die.net/man/
https://elixir.bootlin.com/linux/
https://elixir.bootlin.com/musl/
https://elixir.bootlin.com/glibc/

Anonymous
03/05/26(Thu)11:25:03 No.108302139

Anonymous 03/05/26(Thu)11:25:03 No.108302139

The name is bizarre, but how else would you enlarge a file that you only ever map into your process? If you don't write() to it it never gets bigger.

Hence the ftruncate.

Anonymous
03/05/26(Thu)16:15:09 No.108304274

Anonymous 03/05/26(Thu)16:15:09 No.108304274

Bump.

Anonymous
03/05/26(Thu)17:23:31 No.108304766

Anonymous 03/05/26(Thu)17:23:31 No.108304766

>>108302139
It could feasibly creat a file with some specific length argument.
What you can actually do is lseek to some arbitrary location and then do a single write, although that is quite the hack.

Anonymous
03/05/26(Thu)17:25:36 No.108304780

Anonymous 03/05/26(Thu)17:25:36 No.108304780

>>108301681
>only other thing i will add is it's pretty bizarre (from a naming perspective) that you can "truncate" a file to a larger size
This will also create a "sparse" file with "holes" that doesn't take up its full size on disk.

Anonymous
03/05/26(Thu)20:12:34 No.108305923

Anonymous 03/05/26(Thu)20:12:34 No.108305923

bampu

Anonymous
03/05/26(Thu)21:29:35 No.108306464

Anonymous 03/05/26(Thu)21:29:35 No.108306464

>>108302139
i would just rename it to like fsetsize lol

Anonymous
03/05/26(Thu)23:06:03 No.108307128

Anonymous 03/05/26(Thu)23:06:03 No.108307128

>>108304766
Yeah. Sure. Issue two syscalls, with the second one potentially triggering a block.

Autism?

Anonymous
03/05/26(Thu)23:08:05 No.108307145

Anonymous 03/05/26(Thu)23:08:05 No.108307145

>>108301681
do poll() tomorrow

Anonymous
03/06/26(Fri)01:14:57 No.108307662

Anonymous 03/06/26(Fri)01:14:57 No.108307662

>>108307145
already did poll like a month and a half ago, sorry

Anonymous
03/06/26(Fri)02:08:58 No.108307919

Anonymous 03/06/26(Fri)02:08:58 No.108307919

>>108304766
>It could feasibly creat a file with some specific length argument.
It could feasibly be done with/as capability of creat to create file with some specific length argument.
>>108307128
the other anon asked how else you could possibly size a file. There's your answer. The autism seems to be strong on your side, rather
>>108307145
what do you want to talk about

Anonymous
03/06/26(Fri)02:43:16 No.108308093

Anonymous 03/06/26(Fri)02:43:16 No.108308093

>>108307919
>you're autistic because you mind mode switches and thread blocks
So not only autism on your side, but also retardation.
But then again your spelling gives it away.

Anonymous
03/06/26(Fri)06:01:05 No.108309059

Anonymous 03/06/26(Fri)06:01:05 No.108309059

>>108308093
no, the autism is on your side because rather than actually talk about merits you instead opt to insult other people.
speaks very highly of you indeed, grow up. I can't really describe how pathetic I consider you and your ilk
>spelling gives it away
?

Anonymous
03/06/26(Fri)09:37:28 No.108310111

Anonymous 03/06/26(Fri)09:37:28 No.108310111

i'll give us another bampu