Do typical system call interfaces allow reducing the size of a file (without replacing it with a different...
Is there a way to open() a file and cause it to shrink? One can, of course, open them in append-mode or seek to the end and write to cause them to grow. However, as far as I know, there is no method to shrink a file via typical unix-style system call interfaces.
The only way to do so, as far as I know, is by faking it by creating a new shorter file and rename() it in place of the older one.
I just wanted confirmation, because I saw an answer that implied that it was possible to make file editors that worked directly on a file instead of going through the process of making a new one and renaming it in place.
I've always thought that the file api in libc and unix-style system call interfaces did not allow for the shrinking of files to ease implementation of filesystems and maybe avoid usage patterns that might contribute to fragmentation.
files filesystems
asked 4 hours ago
JoLJoL
1,096311
add a comment |
Is there a way to open() a file and cause it to shrink? One can, of course, open them in append-mode or seek to the end and write to cause them to grow. However, as far as I know, there is no method to shrink a file via typical unix-style system call interfaces.
The only way to do so, as far as I know, is by faking it by creating a new shorter file and rename() it in place of the older one.
I just wanted confirmation, because I saw an answer that implied that it was possible to make file editors that worked directly on a file instead of going through the process of making a new one and renaming it in place.
I've always thought that the file api in libc and unix-style system call interfaces did not allow for the shrinking of files to ease implementation of filesystems and maybe avoid usage patterns that might contribute to fragmentation.
files filesystems
asked 4 hours ago
JoLJoL
1,096311
add a comment |
Is there a way to open() a file and cause it to shrink? One can, of course, open them in append-mode or seek to the end and write to cause them to grow. However, as far as I know, there is no method to shrink a file via typical unix-style system call interfaces.
The only way to do so, as far as I know, is by faking it by creating a new shorter file and rename() it in place of the older one.
I just wanted confirmation, because I saw an answer that implied that it was possible to make file editors that worked directly on a file instead of going through the process of making a new one and renaming it in place.
I've always thought that the file api in libc and unix-style system call interfaces did not allow for the shrinking of files to ease implementation of filesystems and maybe avoid usage patterns that might contribute to fragmentation.
files filesystems
asked 4 hours ago
JoLJoL
1,096311
Is there a way to open() a file and cause it to shrink? One can, of course, open them in append-mode or seek to the end and write to cause them to grow. However, as far as I know, there is no method to shrink a file via typical unix-style system call interfaces.
The only way to do so, as far as I know, is by faking it by creating a new shorter file and rename() it in place of the older one.
I just wanted confirmation, because I saw an answer that implied that it was possible to make file editors that worked directly on a file instead of going through the process of making a new one and renaming it in place.
I've always thought that the file api in libc and unix-style system call interfaces did not allow for the shrinking of files to ease implementation of filesystems and maybe avoid usage patterns that might contribute to fragmentation.
files filesystems
files filesystems
asked 4 hours ago
JoLJoL
1,096311
asked 4 hours ago
JoLJoL
1,096311
asked 4 hours ago
JoLJoL
1,096311
asked 4 hours ago
JoLJoL
1,096311
asked 4 hours ago
JoLJoL
1,096311
1,096311
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
man -s 2 ftruncate says
DESCRIPTION
The truncate() and ftruncate() functions cause the regular file
named by path or referenced by fd to be truncated to a size of precisely
length bytes.
...
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, 4.4BSD, SVr4 (these calls first appeared in 4.2BSD).
it goes on to say that if you use ftruncate you must have opened the file for writing, and if you use truncate the file must be writable.
answered 4 hours ago
icarusicarus
5,8361929
add a comment |
Your Answer
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "106"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f496104%2fdo-typical-system-call-interfaces-allow-reducing-the-size-of-a-file-without-rep%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
man -s 2 ftruncate says
DESCRIPTION
The truncate() and ftruncate() functions cause the regular file
named by path or referenced by fd to be truncated to a size of precisely
length bytes.
...
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, 4.4BSD, SVr4 (these calls first appeared in 4.2BSD).
it goes on to say that if you use ftruncate you must have opened the file for writing, and if you use truncate the file must be writable.
answered 4 hours ago
icarusicarus
5,8361929
add a comment |
man -s 2 ftruncate says
DESCRIPTION
The truncate() and ftruncate() functions cause the regular file
named by path or referenced by fd to be truncated to a size of precisely
length bytes.
...
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, 4.4BSD, SVr4 (these calls first appeared in 4.2BSD).
it goes on to say that if you use ftruncate you must have opened the file for writing, and if you use truncate the file must be writable.
answered 4 hours ago
icarusicarus
5,8361929
add a comment |
man -s 2 ftruncate says
DESCRIPTION
The truncate() and ftruncate() functions cause the regular file
named by path or referenced by fd to be truncated to a size of precisely
length bytes.
...
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, 4.4BSD, SVr4 (these calls first appeared in 4.2BSD).
it goes on to say that if you use ftruncate you must have opened the file for writing, and if you use truncate the file must be writable.
answered 4 hours ago
icarusicarus
5,8361929
man -s 2 ftruncate says
DESCRIPTION
The truncate() and ftruncate() functions cause the regular file
named by path or referenced by fd to be truncated to a size of precisely
length bytes.
...
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, 4.4BSD, SVr4 (these calls first appeared in 4.2BSD).
it goes on to say that if you use ftruncate you must have opened the file for writing, and if you use truncate the file must be writable.
answered 4 hours ago
icarusicarus
5,8361929
answered 4 hours ago
icarusicarus
5,8361929
answered 4 hours ago
icarusicarus
5,8361929
answered 4 hours ago
icarusicarus
5,8361929
5,8361929
add a comment |
add a comment |
Thanks for contributing an answer to Unix & Linux Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f496104%2fdo-typical-system-call-interfaces-allow-reducing-the-size-of-a-file-without-rep%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
