Solved the problem for never return the last line if it's not followed by a newline by Code-Hex · Pull Request #126 · hpcloud/tail

Code-Hex · 2017-07-24T09:47:34Z

What was the problem?

Even though enable the Follow mode, Could not get the last line if it is not newline on end of the line.

For example, I had read the file that is not followed by a newline on the last line using github.com/hpcloud/tail. file is like this.

host:192.168.12.34	user:-	time:2015-09-06T05:58:05+09:00	method:POST	uri:/foo/bar?token=xxx&uuid=1234	protocol:HTTP/1.1	status:200	size:12	api_status:-	request_time:0.247	apptime:0.057	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T05:58:41+09:00	method:POST	uri:/foo/bar?token=yyy	protocol:HTTP/1.1	status:200	size:34	api_status:-	request_time:0.012	apptime:0.100	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:42+09:00	method:GET	uri:/foo/bar?token=zzz	protocol:HTTP/1.1	status:200	size:56	api_status:-	request_time:0.034	apptime:0.123	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:43+09:00	method:GET	uri:/foo/bar	protocol:HTTP/1.1	status:400	size:15	api_status:-	request_time:-	apptime:-	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T05:58:44+09:00	method:POST	uri:/foo/bar?token=yyy	protocol:HTTP/1.1	status:200	size:34	api_status:-	request_time:0.123	apptime:0.234	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T05:58:44+09:00	method:POST	uri:/hoge/piyo?id=yyy	protocol:HTTP/1.1	status:200	size:34	api_status:-	request_time:0.123	apptime:0.234	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T05:58:05+09:00	method:POST	uri:/foo/bar?token=xxx&uuid=1234	protocol:HTTP/1.1	status:200	size:12	api_status:-	request_time:0.247	apptime:0.057	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T05:58:41+09:00	method:POST	uri:/foo/bar?token=yyy	protocol:HTTP/1.1	status:200	size:34	api_status:-	request_time:0.012	apptime:0.100	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:42+09:00	method:GET	uri:/foo/bar?token=zzz	protocol:HTTP/1.1	status:200	size:56	api_status:-	request_time:0.034	apptime:0.123	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:43+09:00	method:GET	uri:/foo/bar	protocol:HTTP/1.1	status:400	size:15	api_status:-	request_time:-	apptime:-	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:43+09:00	method:GET	uri:/diary/entry/1234	protocol:HTTP/1.1	status:200	size:15	api_status:-	request_time:-	apptime:0.135	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:43+09:00	method:GET	uri:/diary/entry/5678	protocol:HTTP/1.1	status:200	size:30	api_status:-	request_time:-	apptime:0.432	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:42+09:00	method:GET	uri:/foo/bar?token=zzz	protocol:HTTP/1.1	status:200	size:56	api_status:-	request_time:0.034	apptime:0.123	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:43+09:00	method:GET	uri:/foo/bar	protocol:HTTP/1.1	status:400	size:15	api_status:-	request_time:-	apptime:-	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:43+09:00	method:GET	uri:/diary/entry/1234	protocol:HTTP/1.1	status:200	size:15	api_status:-	request_time:-	apptime:0.135	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:43+09:00	method:GET	uri:/diary/entry/5678	protocol:HTTP/1.1	status:200	size:30	api_status:-	request_time:-	apptime:0.432	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T05:58:05+09:00	method:POST	uri:/foo/bar?token=xxx&uuid=1234	protocol:HTTP/1.1	status:200	size:12	api_status:-	request_time:0.247	apptime:0.057	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-  user_id:-
host:192.168.12.34	user:-	time:2015-09-06T05:58:41+09:00	method:POST	uri:/foo/bar?token=yyy	protocol:HTTP/1.1	status:200	size:34	api_status:-	request_time:0.012	apptime:0.100	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:42+09:00	method:GET	uri:/foo/bar?token=zzz	protocol:HTTP/1.1	status:200	size:56	api_status:-	request_time:0.034	apptime:0.123	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:43+09:00	method:GET	uri:/foo/bar	protocol:HTTP/1.1	status:400	size:15	api_status:-	request_time:-	apptime:-	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:43+09:00	method:GET	uri:/foo/bar	protocol:HTTP/1.1	status:400	size:15	api_status:-	request_time:-	apptime:-	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2	uuid:-	user_id:-
host:192.168.12.34	user:-	time:2015-09-06T06:00:43+09:00	method:GET	uri:/foo/bar	protocol:HTTP/1.1	status:400	size:15	api_status:-	request_time:-	apptime:-	upstream_addr:127.0.0.1:12345	referer:-	user_agent:curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.4 libidn/1.18 libssh2/1.4.3	uuid:-	user_id:-

But, when I use tail -f, I could get the the last line.
We must need to fix this problem.

Thank you.

… by a newline

Code-Hex · 2017-07-25T01:57:01Z

I think you should not trim newline from the line when write to file.
https://github.com/Code-Hex/tail/blob/5ad6447941c464f021ac1c2475ddb04a6e2caf47/tail.go#L221

Because, We can think about these cases.
This code compare with tail -f.

for line := range t.Lines {
    fmt.Println(line.Text)
}

I am going to write a some messages.

% printf "hello\n" >> a.txt
% printf wor >> a.txt
% printf "ld\n" >> a.txt

Result,

# tail -f
hello
world(Displayed `ld` after once time displayed `wor`)

# hpcloud/tail
hello
world(It is displayed `world` at once)

# Code-Hex/tail
hello
wor(newlined)
ld

So, If you deleted code to trim the newline, We can get the correct result like follow this.

for line := range t.Lines {
    fmt.Print(line.Text)
}

Then,

# tail -f
hello
world(Displayed `ld` after once time displayed `wor`)

# After remove code to trim newline from the line.
hello
world(Displayed `ld` after once time displayed `wor`)

Code-Hex added 3 commits July 24, 2017 17:37

Decreased defers

90586ec

Fixed a potential to never return the last line if it is not followed…

c153685

… by a newline

Fixed test

5ad6447

nxadm mentioned this pull request Sep 8, 2019

Overview of reviewed/applied open Pull Requests of the dormant upstream project by nxadm/tail nxadm/tail#5

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nxadm mentioned this pull request Jan 24, 2021

Overview of reviewed/fixed/applied issues/PRs of the abandoned upstream (fixed on nxadm/tail) nxadm/tail#6

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73 tasks

kokes mentioned this pull request Mar 29, 2021

Cannot determine if a given line is complete or not nxadm/tail#25

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Solved the problem for never return the last line if it's not followed by a newline#126

Solved the problem for never return the last line if it's not followed by a newline#126
Code-Hex wants to merge 3 commits intohpcloud:masterfrom
Code-Hex:master

Code-Hex commented Jul 24, 2017 •

edited

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Code-Hex commented Jul 25, 2017

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Code-Hex commented Jul 24, 2017 •

edited

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