{"id":10806,"date":"2024-12-12T06:33:56","date_gmt":"2024-12-12T06:33:56","guid":{"rendered":"https:\/\/blog.webystrata.co.uk\/?p=10806"},"modified":"2024-12-12T06:33:56","modified_gmt":"2024-12-12T06:33:56","slug":"how-to-read-and-edit-files-in-linux","status":"publish","type":"post","link":"https:\/\/www.webystrata.co.uk\/blog\/how-to-read-and-edit-files-in-linux\/","title":{"rendered":"How to Read and Edit Files in Linux"},"content":{"rendered":"

\"How<\/a><\/h1>\n

How to Read and Edit Files in Linux<\/h1>\n

This guide is only going to show an overview of the commands. To find out more about each command you can run the following:<\/p>\n

\n
\n
man [<\/span>command]<\/span>\r\n<\/pre>\n<\/div>\n<\/div>\n
There are several ways to output a file in Linux<\/a>.<\/p>\n
Here are two test files and their content, we\u2019ll be using these in the upcoming examples.<\/p>\n
\n
\n
cat fileone.txt\r\n<\/pre>\n<\/div>\n<\/div>\n
\n
\n
one<\/span>\r\ntwo<\/span>\r\nthree<\/span>\r\nfour<\/span>\r\nfive<\/span>\r\n<\/pre>\n<\/div>\n<\/div>\n
\n
\n
cat filetwo.txt\r\n<\/pre>\n<\/div>\n<\/div>\n
\n
\n
ONE<\/span>\r\nTWO<\/span>\r\nTHREE<\/span>\r\nFOUR<\/span>\r\nFIVE<\/span>\r\n<\/pre>\n<\/div>\n<\/div>\n
\n
cat<\/span><\/code><\/h2>\n
cat<\/span><\/code>\u00a0is mostly used today to output a file to the screen.<\/p>\n
\n
\n
[root@c7 ~]# <\/span>cat fileone.txt\r\none<\/span>\r\ntwo<\/span>\r\nthree<\/span>\r\nfour<\/span>\r\nfive<\/span>\r\n<\/pre>\n<\/div>\n<\/div>\n
It was originally to combine the output of two files.<\/p>\n
\n
\n
[root@c7 ~]# <\/span>cat fileone.txt filetwo.txt\r\none<\/span>\r\ntwo<\/span>\r\nthree<\/span>\r\nfour<\/span>\r\nfive<\/span>\r\nONE<\/span>\r\nTWO<\/span>\r\nTHREE<\/span>\r\nFOUR<\/span>\r\nFIVE<\/span>\r\n<\/pre>\n<\/div>\n<\/div>\n
It can be used to add content to a file.<\/p>\n
\n
\n
[root@c7 ~]# <\/span>cat > filethree.txt\r\nnew file content<\/span>\r\n^C<\/span>\r\n[root@c7 ~]# <\/span>cat filethree.txt\r\nnew file content<\/span>\r\n<\/pre>\n<\/div>\n<\/div>\n
After the\u00a0cat<\/span>\u00a0><\/span>\u00a0filethree.txt<\/span><\/code>\u00a0command, press enter and enter the text you want to add to your file. End this with a new line and\u00a0ctrl<\/span>\u00a0+<\/span>\u00a0c<\/span><\/code>.<\/p>\n
\n
This command will\u00a0NOT<\/strong>\u00a0tell you if the file already exists so it\u2019s very easy to overwrite a file. Use with care.<\/p>\n<\/div>\n<\/section>\n
\n
`less<\/h2>\n
For<\/span>\u00a0very<\/span>\u00a0large<\/span>\u00a0files<\/span>\u00a0less<\/span>\u00a0will<\/span>\u00a0allow<\/span>\u00a0you<\/span>\u00a0to<\/span>\u00a0scroll<\/span>\u00a0up<\/span>\u00a0and<\/span>\u00a0down<\/span>\u00a0a<\/span>\u00a0file.<\/span>\u00a0Search<\/span>\u00a0the<\/span>\u00a0file<\/span>\u00a0with<\/span>\u00a0the<\/span><\/code>\/searchtermkeys.<\/span>\u00a0Use<\/span>\u00a0the<\/span><\/code>n` key to keep searching.<\/p>\n<\/section>\n
\n
head<\/span><\/code><\/h2>\n
By default\u00a0head<\/span><\/code>\u00a0will show the top 10 lines of a file. This can be adjusted with the\u00a0-n<\/span><\/code>\u00a0flag.<\/p>\n
\n
\n
[root@c7 ~]# <\/span>head -n 2<\/span> fileone.txt\r\none<\/span>\r\ntwo<\/span>\r\n<\/pre>\n<\/div>\n<\/div>\n<\/section>\n
\n
tail<\/span><\/code><\/h2>\n
By default\u00a0tail<\/span><\/code>\u00a0will show the bottom 10 lines of a file. This can adjusted with the\u00a0-n<\/span><\/code>\u00a0flag.<\/p>\n
\n
\n
[root@c7 ~]# <\/span>tail -n 2<\/span> fileone.txt\r\nfour<\/span>\r\nfive<\/span>\r\n<\/pre>\n<\/div>\n<\/div>\n
If your file is changing, you can watch the output. This is best used on logs like mail logs.<\/p>\n
\n
\n
[root@c7 ~]# <\/span>tail -f \/var\/log\/maillog\r\nAug 10 00:00:21 c7 sSMTP[31684]: Unable to locate mail<\/span>\r\nAug 10 00:00:21 c7 sSMTP[31684]: Cannot open mail:25<\/span>\r\nAug 10 11:10:44 c7 postfix\/postqueue[23404]: fatal: Cannot flush mail queue - mail system is down<\/span>\r\nAug 10 11:10:54 c7 postfix\/postfix-script[23546]: starting the Postfix mail system<\/span>\r\nAug 10 11:10:54 c7 postfix\/master[23548]: daemon started -- version 2.10.1, configuration \/etc\/postfix<\/span>\r\nAug 11 00:00:07 c7 sSMTP[25365]: Unable to locate mail<\/span>\r\nAug 11 00:00:07 c7 sSMTP[25365]: Cannot open mail:25<\/span>\r\nAug 11 11:17:21 c7 postfix\/smtpd[9292]: connect from localhost[::1]<\/span>\r\nAug 11 11:18:32 c7 postfix\/smtpd[9292]: lost connection after CONNECT from localhost[::1]<\/span>\r\nAug 11 11:18:32 c7 postfix\/smtpd[9292]: disconnect from localhost[::1]<\/span><\/pre>\n<\/div>\n<\/div>\n<\/section>\n","protected":false},"excerpt":{"rendered":"
How to Read and Edit Files in Linux This guide is only going to show an overview of the commands. To find out more about each command you can run the following: man [command] There are several ways to output a file in Linux. Here are two test files and their content, we\u2019ll be using […]<\/p>\n","protected":false},"author":1,"featured_media":10808,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[],"class_list":["post-10806","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-linux"],"_links":{"self":[{"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/posts\/10806","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/comments?post=10806"}],"version-history":[{"count":3,"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/posts\/10806\/revisions"}],"predecessor-version":[{"id":10810,"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/posts\/10806\/revisions\/10810"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/media\/10808"}],"wp:attachment":[{"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/media?parent=10806"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/categories?post=10806"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.webystrata.co.uk\/blog\/wp-json\/wp\/v2\/tags?post=10806"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}