What is the use of option -u in the Linux cat command?
In the man page of cat, -u means (ignored)
[raj@localhost zzz]$ cat file1
hello world
1 2 3 4 5 6 7 8 9 0
! @ # $ % ^ & * ( ) _ + ~ ` ; ' , .{ } [ ] = | / -
[raj@localhost zzz]$ cat -u file1
hello world
1 2 3 4 5 6 7 8 9 0
! @ # $ % ^ & * ( ) _ + ~ ` ; ' , .{ } [ ] = | / -
When should we use the -u option?
And what it will ignore?
linux centos-6
edited Jul 29 '15 at 19:27
Hennes
58.8k792141
asked Aug 24 '12 at 10:20
max
2,48994261
add a comment |
In the man page of cat, -u means (ignored)
[raj@localhost zzz]$ cat file1
hello world
1 2 3 4 5 6 7 8 9 0
! @ # $ % ^ & * ( ) _ + ~ ` ; ' , .{ } [ ] = | / -
[raj@localhost zzz]$ cat -u file1
hello world
1 2 3 4 5 6 7 8 9 0
! @ # $ % ^ & * ( ) _ + ~ ` ; ' , .{ } [ ] = | / -
When should we use the -u option?
And what it will ignore?
linux centos-6
edited Jul 29 '15 at 19:27
Hennes
58.8k792141
asked Aug 24 '12 at 10:20
max
2,48994261
add a comment |
In the man page of cat, -u means (ignored)
[raj@localhost zzz]$ cat file1
hello world
1 2 3 4 5 6 7 8 9 0
! @ # $ % ^ & * ( ) _ + ~ ` ; ' , .{ } [ ] = | / -
[raj@localhost zzz]$ cat -u file1
hello world
1 2 3 4 5 6 7 8 9 0
! @ # $ % ^ & * ( ) _ + ~ ` ; ' , .{ } [ ] = | / -
When should we use the -u option?
And what it will ignore?
linux centos-6
edited Jul 29 '15 at 19:27
Hennes
58.8k792141
asked Aug 24 '12 at 10:20
max
2,48994261
In the man page of cat, -u means (ignored)
[raj@localhost zzz]$ cat file1
hello world
1 2 3 4 5 6 7 8 9 0
! @ # $ % ^ & * ( ) _ + ~ ` ; ' , .{ } [ ] = | / -
[raj@localhost zzz]$ cat -u file1
hello world
1 2 3 4 5 6 7 8 9 0
! @ # $ % ^ & * ( ) _ + ~ ` ; ' , .{ } [ ] = | / -
When should we use the -u option?
And what it will ignore?
linux centos-6
linux centos-6
edited Jul 29 '15 at 19:27
Hennes
58.8k792141
asked Aug 24 '12 at 10:20
max
2,48994261
edited Jul 29 '15 at 19:27
Hennes
58.8k792141
asked Aug 24 '12 at 10:20
max
2,48994261
edited Jul 29 '15 at 19:27
Hennes
58.8k792141
edited Jul 29 '15 at 19:27
Hennes
58.8k792141
edited Jul 29 '15 at 19:27
Hennes
58.8k792141
58.8k792141
asked Aug 24 '12 at 10:20
max
2,48994261
asked Aug 24 '12 at 10:20
max
2,48994261
asked Aug 24 '12 at 10:20
max
2,48994261
2,48994261
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
The option -u is so that cat and hence Unix/Linux is POSIX compliant. The specification says:
The following option shall be supported:
-u Write bytes from the input file to the standard output without delay as each is read.
In practice, cat does this automatically and there's no way to turn it off so the option is accepted but ignored as it has no effect on the behaviour.
answered Aug 24 '12 at 12:21
StarNamer
835515
add a comment |
The option itself is being ignored. It probably existed in older or different versions of cat, so it does not end in an error if an older script uses it, but it does not change cat's behaviour in any way.
answered Aug 24 '12 at 10:25
choroba
12.9k13039
add a comment |
Your Answer
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "3"
};
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: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
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%2fsuperuser.com%2fquestions%2f465785%2fwhat-is-the-use-of-option-u-in-the-linux-cat-command%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
The option -u is so that cat and hence Unix/Linux is POSIX compliant. The specification says:
The following option shall be supported:
-u Write bytes from the input file to the standard output without delay as each is read.
In practice, cat does this automatically and there's no way to turn it off so the option is accepted but ignored as it has no effect on the behaviour.
answered Aug 24 '12 at 12:21
StarNamer
835515
add a comment |
The option -u is so that cat and hence Unix/Linux is POSIX compliant. The specification says:
The following option shall be supported:
-u Write bytes from the input file to the standard output without delay as each is read.
In practice, cat does this automatically and there's no way to turn it off so the option is accepted but ignored as it has no effect on the behaviour.
answered Aug 24 '12 at 12:21
StarNamer
835515
add a comment |
The option -u is so that cat and hence Unix/Linux is POSIX compliant. The specification says:
The following option shall be supported:
-u Write bytes from the input file to the standard output without delay as each is read.
In practice, cat does this automatically and there's no way to turn it off so the option is accepted but ignored as it has no effect on the behaviour.
answered Aug 24 '12 at 12:21
StarNamer
835515
The option -u is so that cat and hence Unix/Linux is POSIX compliant. The specification says:
The following option shall be supported:
-u Write bytes from the input file to the standard output without delay as each is read.
In practice, cat does this automatically and there's no way to turn it off so the option is accepted but ignored as it has no effect on the behaviour.
answered Aug 24 '12 at 12:21
StarNamer
835515
answered Aug 24 '12 at 12:21
StarNamer
835515
answered Aug 24 '12 at 12:21
StarNamer
835515
answered Aug 24 '12 at 12:21
StarNamer
835515
835515
add a comment |
add a comment |
The option itself is being ignored. It probably existed in older or different versions of cat, so it does not end in an error if an older script uses it, but it does not change cat's behaviour in any way.
answered Aug 24 '12 at 10:25
choroba
12.9k13039
add a comment |
The option itself is being ignored. It probably existed in older or different versions of cat, so it does not end in an error if an older script uses it, but it does not change cat's behaviour in any way.
answered Aug 24 '12 at 10:25
choroba
12.9k13039
add a comment |
The option itself is being ignored. It probably existed in older or different versions of cat, so it does not end in an error if an older script uses it, but it does not change cat's behaviour in any way.
answered Aug 24 '12 at 10:25
choroba
12.9k13039
The option itself is being ignored. It probably existed in older or different versions of cat, so it does not end in an error if an older script uses it, but it does not change cat's behaviour in any way.
answered Aug 24 '12 at 10:25
choroba
12.9k13039
answered Aug 24 '12 at 10:25
choroba
12.9k13039
answered Aug 24 '12 at 10:25
choroba
12.9k13039
answered Aug 24 '12 at 10:25
choroba
12.9k13039
12.9k13039
add a comment |
add a comment |
Thanks for contributing an answer to Super User!
- 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.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- 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%2fsuperuser.com%2fquestions%2f465785%2fwhat-is-the-use-of-option-u-in-the-linux-cat-command%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
