tail and grep + print and exit first match

I'm looking for a 1 liner to tail a file and grep a "string", print the first match (new line) and exit.

I came up with:

tail -f /var/log/logfile.log -n 0 | grep -m 1 -i string_to_match

actual result is that the command prints the first match but exits only after the second match.
any help would be appreciated

edited Jan 2 at 8:11

tripleee

93.7k13130185

asked Jan 1 at 8:47

Isaac A

186

Please take a look at How to create a Minimal, Complete, and Verifiable example. Please add sample input and your desired output for that sample input to your question.

– Cyrus
Jan 1 at 8:52

See this: stackoverflow.com/questions/5024357/… which also has a link to Superuser with more solutions.

– James Brown
Jan 1 at 9:42

1

Heh. So, grep exits immediately, but tail doesn't know that grep exited until it tries to write a second line and gets a SIGPIPE.

– Charles Duffy
Jan 1 at 16:17

add a comment |

I'm looking for a 1 liner to tail a file and grep a "string", print the first match (new line) and exit.

I came up with:

tail -f /var/log/logfile.log -n 0 | grep -m 1 -i string_to_match

actual result is that the command prints the first match but exits only after the second match.
any help would be appreciated

edited Jan 2 at 8:11

tripleee

93.7k13130185

asked Jan 1 at 8:47

Isaac A

186

Please take a look at How to create a Minimal, Complete, and Verifiable example. Please add sample input and your desired output for that sample input to your question.

– Cyrus
Jan 1 at 8:52

See this: stackoverflow.com/questions/5024357/… which also has a link to Superuser with more solutions.

– James Brown
Jan 1 at 9:42

1

Heh. So, grep exits immediately, but tail doesn't know that grep exited until it tries to write a second line and gets a SIGPIPE.

– Charles Duffy
Jan 1 at 16:17

add a comment |

I'm looking for a 1 liner to tail a file and grep a "string", print the first match (new line) and exit.

I came up with:

tail -f /var/log/logfile.log -n 0 | grep -m 1 -i string_to_match

actual result is that the command prints the first match but exits only after the second match.
any help would be appreciated

edited Jan 2 at 8:11

tripleee

93.7k13130185

asked Jan 1 at 8:47

Isaac A

186

I'm looking for a 1 liner to tail a file and grep a "string", print the first match (new line) and exit.

I came up with:

tail -f /var/log/logfile.log -n 0 | grep -m 1 -i string_to_match

actual result is that the command prints the first match but exits only after the second match.
any help would be appreciated

linux bash grep tail

edited Jan 2 at 8:11

tripleee

93.7k13130185

asked Jan 1 at 8:47

Isaac A

186

edited Jan 2 at 8:11

tripleee

93.7k13130185

asked Jan 1 at 8:47

Isaac A

186

edited Jan 2 at 8:11

tripleee

93.7k13130185

edited Jan 2 at 8:11

tripleee

93.7k13130185

edited Jan 2 at 8:11

tripleee

93.7k13130185

asked Jan 1 at 8:47

Isaac A

186

asked Jan 1 at 8:47

Isaac A

186

asked Jan 1 at 8:47

Isaac A

186

Please take a look at How to create a Minimal, Complete, and Verifiable example. Please add sample input and your desired output for that sample input to your question.

– Cyrus
Jan 1 at 8:52

See this: stackoverflow.com/questions/5024357/… which also has a link to Superuser with more solutions.

– James Brown
Jan 1 at 9:42

1

Heh. So, grep exits immediately, but tail doesn't know that grep exited until it tries to write a second line and gets a SIGPIPE.

– Charles Duffy
Jan 1 at 16:17

add a comment |

Please take a look at How to create a Minimal, Complete, and Verifiable example. Please add sample input and your desired output for that sample input to your question.

– Cyrus
Jan 1 at 8:52

See this: stackoverflow.com/questions/5024357/… which also has a link to Superuser with more solutions.

– James Brown
Jan 1 at 9:42

1

Heh. So, grep exits immediately, but tail doesn't know that grep exited until it tries to write a second line and gets a SIGPIPE.

– Charles Duffy
Jan 1 at 16:17

Please take a look at How to create a Minimal, Complete, and Verifiable example. Please add sample input and your desired output for that sample input to your question.

– Cyrus
Jan 1 at 8:52

See this: stackoverflow.com/questions/5024357/… which also has a link to Superuser with more solutions.

– James Brown
Jan 1 at 9:42

Heh. So, grep exits immediately, but tail doesn't know that grep exited until it tries to write a second line and gets a SIGPIPE.

– Charles Duffy
Jan 1 at 16:17

add a comment |

1 Answer
1

active

oldest

votes

In Bash you could use:

$ grep -m 1 string_to_match <(tail -n 0 -f file)

This could work for testing (NOTICE: IT APPENDS TO A FILE NAMED file):

$ grep -m 1 foo <(tail -n 0 -f file) & sleep 2 ; echo -e bar\nfoo >> file

[1] 5390

foo

[1]+  Done                    grep --color -m 1 foo <(tail -n 0 -f file)

Edit: Further testing revealed that tail stays running in the background but exits after the next line in the file.

edited Jan 1 at 11:46

answered Jan 1 at 9:08

James Brown

19.4k31736

Humm, pretty hard to make a one-liner for testing.

– James Brown
Jan 1 at 9:11

thanks, this one gives syntax error near unexpected token `('

– Isaac A
Jan 1 at 9:13

1

@IsaacA: You don't use bash.

– Cyrus
Jan 1 at 9:15

1

@IsaacA: I can't reproduce the error you mentioned with bash-3.2.57. It occurs when using sh.

– Cyrus
Jan 1 at 9:52

1

@JamesBrown Eventually what you suggested was the right answer for me! Thanks and thank you all! grep -m 1 string_to_match <(tail -n 0 -f /var/log/syslog.log)

– Isaac A
Jan 2 at 8:03

|
show 4 more comments

Your Answer

StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
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
});

}
});

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53994136%2ftail-and-grep-print-and-exit-first-match%23new-answer', 'question_page');
}
);

Post as a guest

Name

Required, but never shown

1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

In Bash you could use:

$ grep -m 1 string_to_match <(tail -n 0 -f file)

This could work for testing (NOTICE: IT APPENDS TO A FILE NAMED file):

$ grep -m 1 foo <(tail -n 0 -f file) & sleep 2 ; echo -e bar\nfoo >> file

[1] 5390

foo

[1]+  Done                    grep --color -m 1 foo <(tail -n 0 -f file)

Edit: Further testing revealed that tail stays running in the background but exits after the next line in the file.

edited Jan 1 at 11:46

answered Jan 1 at 9:08

James Brown

19.4k31736

Humm, pretty hard to make a one-liner for testing.

– James Brown
Jan 1 at 9:11

thanks, this one gives syntax error near unexpected token `('

– Isaac A
Jan 1 at 9:13

1

@IsaacA: You don't use bash.

– Cyrus
Jan 1 at 9:15

1

@IsaacA: I can't reproduce the error you mentioned with bash-3.2.57. It occurs when using sh.

– Cyrus
Jan 1 at 9:52

1

@JamesBrown Eventually what you suggested was the right answer for me! Thanks and thank you all! grep -m 1 string_to_match <(tail -n 0 -f /var/log/syslog.log)

– Isaac A
Jan 2 at 8:03

|
show 4 more comments

In Bash you could use:

$ grep -m 1 string_to_match <(tail -n 0 -f file)

This could work for testing (NOTICE: IT APPENDS TO A FILE NAMED file):

$ grep -m 1 foo <(tail -n 0 -f file) & sleep 2 ; echo -e bar\nfoo >> file

[1] 5390

foo

[1]+  Done                    grep --color -m 1 foo <(tail -n 0 -f file)

Edit: Further testing revealed that tail stays running in the background but exits after the next line in the file.

edited Jan 1 at 11:46

answered Jan 1 at 9:08

James Brown

19.4k31736

Humm, pretty hard to make a one-liner for testing.

– James Brown
Jan 1 at 9:11

thanks, this one gives syntax error near unexpected token `('

– Isaac A
Jan 1 at 9:13

1

@IsaacA: You don't use bash.

– Cyrus
Jan 1 at 9:15

1

@IsaacA: I can't reproduce the error you mentioned with bash-3.2.57. It occurs when using sh.

– Cyrus
Jan 1 at 9:52

1

@JamesBrown Eventually what you suggested was the right answer for me! Thanks and thank you all! grep -m 1 string_to_match <(tail -n 0 -f /var/log/syslog.log)

– Isaac A
Jan 2 at 8:03

|
show 4 more comments

In Bash you could use:

$ grep -m 1 string_to_match <(tail -n 0 -f file)

This could work for testing (NOTICE: IT APPENDS TO A FILE NAMED file):

$ grep -m 1 foo <(tail -n 0 -f file) & sleep 2 ; echo -e bar\nfoo >> file

[1] 5390

foo

[1]+  Done                    grep --color -m 1 foo <(tail -n 0 -f file)

Edit: Further testing revealed that tail stays running in the background but exits after the next line in the file.

edited Jan 1 at 11:46

answered Jan 1 at 9:08

James Brown

19.4k31736

In Bash you could use:

$ grep -m 1 string_to_match <(tail -n 0 -f file)

This could work for testing (NOTICE: IT APPENDS TO A FILE NAMED file):

$ grep -m 1 foo <(tail -n 0 -f file) & sleep 2 ; echo -e bar\nfoo >> file

[1] 5390

foo

[1]+  Done                    grep --color -m 1 foo <(tail -n 0 -f file)

Edit: Further testing revealed that tail stays running in the background but exits after the next line in the file.

edited Jan 1 at 11:46

answered Jan 1 at 9:08

James Brown

19.4k31736

edited Jan 1 at 11:46

answered Jan 1 at 9:08

James Brown

19.4k31736

answered Jan 1 at 9:08

James Brown

19.4k31736

answered Jan 1 at 9:08

James Brown

19.4k31736

Humm, pretty hard to make a one-liner for testing.

– James Brown
Jan 1 at 9:11

thanks, this one gives syntax error near unexpected token `('

– Isaac A
Jan 1 at 9:13

1

@IsaacA: You don't use bash.

– Cyrus
Jan 1 at 9:15

1

@IsaacA: I can't reproduce the error you mentioned with bash-3.2.57. It occurs when using sh.

– Cyrus
Jan 1 at 9:52

1

@JamesBrown Eventually what you suggested was the right answer for me! Thanks and thank you all! grep -m 1 string_to_match <(tail -n 0 -f /var/log/syslog.log)

– Isaac A
Jan 2 at 8:03

|
show 4 more comments

Humm, pretty hard to make a one-liner for testing.

– James Brown
Jan 1 at 9:11

thanks, this one gives syntax error near unexpected token `('

– Isaac A
Jan 1 at 9:13

1

@IsaacA: You don't use bash.

– Cyrus
Jan 1 at 9:15

1

@IsaacA: I can't reproduce the error you mentioned with bash-3.2.57. It occurs when using sh.

– Cyrus
Jan 1 at 9:52

1

@JamesBrown Eventually what you suggested was the right answer for me! Thanks and thank you all! grep -m 1 string_to_match <(tail -n 0 -f /var/log/syslog.log)

– Isaac A
Jan 2 at 8:03

Humm, pretty hard to make a one-liner for testing.

– James Brown
Jan 1 at 9:11

thanks, this one gives syntax error near unexpected token `('

– Isaac A
Jan 1 at 9:13

@IsaacA: You don't use bash.

– Cyrus
Jan 1 at 9:15

@IsaacA: I can't reproduce the error you mentioned with bash-3.2.57. It occurs when using sh.

– Cyrus
Jan 1 at 9:52

@JamesBrown Eventually what you suggested was the right answer for me! Thanks and thank you all! grep -m 1 string_to_match <(tail -n 0 -f /var/log/syslog.log)

– Isaac A
Jan 2 at 8:03

|
show 4 more comments

draft saved

draft discarded

Thanks for contributing an answer to Stack Overflow!

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.

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Name

Required, but never shown

Name

Required, but never shown

This page is only for reference, If you need detailed information, please check here

Search This Blog

Ufyukyu