mirror of https://github.com/Idnan/bash-guide.git
1191 lines
30 KiB
Markdown
1191 lines
30 KiB
Markdown
<p align="center">
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<img src="https://cloud.githubusercontent.com/assets/2059754/24601246/753a7f36-1858-11e7-9d6b-7a0e64fb27f7.png" alt="bash logo"/>
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</p>
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## Содержание
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1. [Основные операции](#1-Основные-операции)
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1.1. [Файловые операции](#11-Файловые-операции)
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1.2. [Текстовые операции](#12-text-operations)
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1.3. [Операции с каталогами](#13-directory-operations)
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1.4. [SSH, системная информация и сетевые операции](#14-ssh-system-info--network-operations)
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1.5. [Операции по мониторингу процессов](#15-process-monitoring-operations)
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2. [Основы программирования в командной строке](#2-basic-shell-programming)
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2.1. [Переменные](#21-variables)
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2.2. [Массивы](#22-array)
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2.3. [Замена строк](#23-string-substitution)
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2.4. [Функции](#24-functions)
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2.5. [Условные выражения](#25-conditionals)
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2.6. [Циклы](#26-loops)
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3. [Трюки](#3-tricks)
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4. [Отладка (Debug)](#4-debugging)
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# 1. Основные операции
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### a. `export`
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Отображает все переменные среды. Если вы хотите получить подробную информацию о конкретной переменной, используйте `echo $VARIABLE_NAME`.
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```bash
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export
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```
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Пример:
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```bash
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$ export
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AWS_HOME=/Users/adnanadnan/.aws
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LANG=en_US.UTF-8
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LC_CTYPE=en_US.UTF-8
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LESS=-R
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$ echo $AWS_HOME
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/Users/adnanadnan/.aws
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```
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### b. `whatis`
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whatis показывает описание для пользовательских команд, системных вызовов, библиотечных функций и другое на страницах руководства.
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```bash
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whatis something
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```
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Пример:
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```bash
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$ whatis bash
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bash (1) - GNU Bourne-Again SHell
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```
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### c. `whereis`
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whereis ищет исполняемые файлы, исходные файлы и страницы руководства, используя базу данных, созданную системой автоматически.
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```bash
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whereis name
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```
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Пример:
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```bash
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$ whereis php
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/usr/bin/php
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```
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### d. `which`
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which ищет исполняемые файлы в каталогах, заданных переменной среды PATH. Эта команда будет печатать полный путь к исполняемому файлу.
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```bash
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which program_name
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```
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Пример:
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```bash
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$ which php
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/c/xampp/php/php
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```
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### e. clear
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Очищает содержимое окна.
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## 1.1. Файловые операции
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<table>
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<tr>
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<td><a href="#a-cat">cat</a></td>
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<td><a href="#b-chmod">chmod</a></td>
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<td><a href="#c-chown">chown</a></td>
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<td><a href="#d-cp">cp</a></td>
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<td><a href="#e-diff">diff</a></td>
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<td><a href="#f-file">file</a></td>
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<td><a href="#g-find">find</a></td>
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<td><a href="#h-gunzip">gunzip</a></td>
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<td><a href="#i-gzcat">gzcat</a></td>
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<td><a href="#j-gzip">gzip</a></td>
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<td><a href="#k-head">head</a></td>
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</tr>
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<tr>
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<td><a href="#l-lpq">lpq</a></td>
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<td><a href="#m-lpr">lpr</a></td>
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<td><a href="#n-lprm">lprm</a></td>
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<td><a href="#o-ls">ls</a></td>
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<td><a href="#p-more">more</a></td>
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<td><a href="#q-mv">mv</a></td>
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<td><a href="#r-rm">rm</a></td>
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<td><a href="#s-tail">tail</a></td>
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<td><a href="#t-touch">touch</a></td>
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</tr>
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</table>
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### a. `cat`
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Может использоваться для следующих целей в UNIX или Linux.
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* Отображение текстовых файлов на экране
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* Копирование текстовых файлов
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* Объединение текстовых файлов
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* Создание новых текстовых файлов
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```bash
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cat filename
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cat file1 file2
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cat file1 file2 > newcombinedfile
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cat < file1 > file2 #copy file1 to file2
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```
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### b. `chmod`
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Команда chmod позволяет вам изменять права на чтение, запись и выполнение для ваших файлов и папок. Для получения дополнительной информации об этой команде пройдите по [ссылке](https://ss64.com/bash/chmod.html).
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```bash
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chmod -options filename
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```
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### c. `chown`
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Команда chown означает «владелец прав и позволяет вам изменять владельца данного файла или папки, которые могут быть пользователем и группой. Пользоваться просто, сначала пользователь (владелец), а затем группа, разделенная двоеточием.
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```bash
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chown -options user:group filename
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```
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### d. `cp`
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Копирует файл из одного места в другое.
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```bash
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cp filename1 filename2
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```
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Где `filename1` является исходным путем к файлу и `filename2` путь назначения к файлу.
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### e. `diff`
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Сравнивает файлы и перечисляет их различия.
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```bash
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diff filename1 filename2
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```
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### f. `file`
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Определяет тип файла.
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```bash
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file filename
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```
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Пример:
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```bash
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$ file index.html
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index.html: HTML document, ASCII text
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```
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### g. `find`
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Поиск файлов в каталоге.
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```bash
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find directory options pattern
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```
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Пример:
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```bash
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$ find . -name README.md
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$ find /home/user1 -name '*.png'
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```
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### h. `gunzip`
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Разархивирует файлы сжатые gzip.
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```bash
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gunzip filename
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```
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### i. `gzcat`
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Позволяет просматривать файлы архива gzipped без необходимости его разархивирования.
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```bash
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gzcat filename
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```
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### j. `gzip`
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Архивирование файлов.
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```bash
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gzip filename
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```
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### k. `head`
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Выводит первые 10 строк файла
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```bash
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head filename
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```
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### l. `lpq`
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Проверка очереди вывода.
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```bash
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lpq
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```
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Пример:
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```bash
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$ lpq
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Rank Owner Job File(s) Total Size
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active adnanad 59 demo 399360 bytes
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1st adnanad 60 (stdin) 0 bytes
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```
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### m. `lpr`
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Печать файла.
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```bash
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lpr filename
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```
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### n. `lprm`
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Удалить что-то из очереди печати.
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```bash
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lprm jobnumber
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```
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### o. `ls`
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Список файлов. `ls` имеет множество опций: `-l` список файлов в 'длинном формате', который содержит точный размер файла, имя владельца файла, который имеет право просматривать его и время последнего изменения. `-a` список файлов, включая скрытые файлы. Для получения дополнительной информации об этой команде перейдите по [ссылке](https://ss64.com/bash/ls.html).
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```bash
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ls option
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```
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Пример:
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<pre>
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$ ls -la
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rwxr-xr-x 33 adnan staff 1122 Mar 27 18:44 .
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drwxrwxrwx 60 adnan staff 2040 Mar 21 15:06 ..
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-rw-r--r--@ 1 adnan staff 14340 Mar 23 15:05 .DS_Store
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-rw-r--r-- 1 adnan staff 157 Mar 25 18:08 .bumpversion.cfg
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-rw-r--r-- 1 adnan staff 6515 Mar 25 18:08 .config.ini
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-rw-r--r-- 1 adnan staff 5805 Mar 27 18:44 .config.override.ini
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drwxr-xr-x 17 adnan staff 578 Mar 27 23:36 .git
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-rwxr-xr-x 1 adnan staff 2702 Mar 25 18:08 .gitignore
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</pre>
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### p. `more`
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Показывает первую часть файла (перемещайтесь нажимая пробел и нажмите q для выхода).
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```bash
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more filename
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```
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### q. `mv`
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Перемещает файл из одного места в другое.
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```bash
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mv filename1 filename2
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```
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Где `filename1` является исходным путем к файлу и `filename2` путь назначения к файлу.
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Также может использоваться для переименования файла.
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```bash
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mv old_name new_name
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```
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### r. `rm`
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Удаляет файл. Использование этой команды для каталога приводит к ошибке.
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`rm: directory: is a directory`
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Чтобы удалить каталог необходимо ввести `-r` который будет рекурсивно удалять содержимое каталога. При желании вы можете использовать `-f` флаг для принудительного удаления, то есть без каких-либо подтверждений и т.д.
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```bash
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rm filename
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```
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### s. `tail`
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Выводит последние 10 строк файла. Используйте `-f` для вывода добавленных данных по мере роста файла.
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```bash
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tail filename
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```
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### t. `touch`
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Обновляет отметки времени создания и изменения файла. Если он не существует, он будет создан.
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```bash
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touch filename
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```
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Пример:
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```bash
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$ touch trick.md
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```
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## 1.2. Text Operations
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<table>
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<tr>
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<td><a href="#a-awk">awk</a></td>
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<td><a href="#b-cut">cut</a></td>
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<td><a href="#c-echo">echo</a></td>
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<td><a href="#d-egrep">egrep</a></td>
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<td><a href="#e-fgrep">fgrep</a></td>
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<td><a href="#f-fmt">fmt</a></td>
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<td><a href="#g-grep">grep</a></td>
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<td><a href="#h-nl">nl</a></td>
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<td><a href="#i-sed">sed</a></td>
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<td><a href="#j-sort">sort</a></td>
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</tr>
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<tr>
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<td><a href="#k-tr">tr</a></td>
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<td><a href="#l-uniq">uniq</a></td>
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<td><a href="#m-wc">wc</a></td>
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</tr>
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</table>
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### a. `awk`
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awk is the most useful command for handling text files. It operates on an entire file line by line. By default it uses whitespace to separate the fields. The most common syntax for awk command is
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```bash
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awk '/search_pattern/ { action_to_take_if_pattern_matches; }' file_to_parse
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```
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Lets take following file `/etc/passwd`. Here's the sample data that this file contains:
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```
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root:x:0:0:root:/root:/usr/bin/zsh
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daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
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bin:x:2:2:bin:/bin:/usr/sbin/nologin
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sys:x:3:3:sys:/dev:/usr/sbin/nologin
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sync:x:4:65534:sync:/bin:/bin/sync
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```
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So now lets get only username from this file. Where `-F` specifies that on which base we are going to separate the fields. In our case it's `:`. `{ print $1 }` means print out the first matching field.
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```bash
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awk -F':' '{ print $1 }' /etc/passwd
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```
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After running the above command you will get following output.
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```
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root
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daemon
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bin
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sys
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sync
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```
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For more detail on how to use `awk`, check following [link](https://www.cyberciti.biz/faq/bash-scripting-using-awk).
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### b. `cut`
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Remove sections from each line of files
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*example.txt*
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```bash
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red riding hood went to the park to play
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```
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*show me columns 2 , 7 , and 9 with a space as a separator*
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```bash
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cut -d " " -f2,7,9 example.txt
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```
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```bash
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riding park play
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```
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### c. `echo`
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Display a line of text
|
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*display "Hello World"*
|
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```bash
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echo Hello World
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```
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```bash
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Hello World
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```
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*display "Hello World" with newlines between words*
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```bash
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echo -ne "Hello\nWorld\n"
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```
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```bash
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Hello
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World
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```
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### d. `egrep`
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Print lines matching a pattern - Extended Expression (alias for: 'grep -E')
|
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*example.txt*
|
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```bash
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Lorem ipsum
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dolor sit amet,
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consetetur
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sadipscing elitr,
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sed diam nonumy
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eirmod tempor
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invidunt ut labore
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et dolore magna
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aliquyam erat, sed
|
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diam voluptua. At
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vero eos et
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accusam et justo
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duo dolores et ea
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rebum. Stet clita
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||
kasd gubergren,
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no sea takimata
|
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sanctus est Lorem
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ipsum dolor sit
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amet.
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```
|
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|
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*display lines that have either "Lorem" or "dolor" in them.*
|
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```bash
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egrep '(Lorem|dolor)' example.txt
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or
|
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grep -E '(Lorem|dolor)' example.txt
|
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```
|
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```bash
|
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Lorem ipsum
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||
dolor sit amet,
|
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et dolore magna
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duo dolores et ea
|
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sanctus est Lorem
|
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ipsum dolor sit
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```
|
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|
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### e. `fgrep`
|
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Print lines matching a pattern - FIXED pattern matching (alias for: 'grep -F')
|
||
|
||
*example.txt*
|
||
```bash
|
||
Lorem ipsum
|
||
dolor sit amet,
|
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consetetur
|
||
sadipscing elitr,
|
||
sed diam nonumy
|
||
eirmod tempor
|
||
foo (Lorem|dolor)
|
||
invidunt ut labore
|
||
et dolore magna
|
||
aliquyam erat, sed
|
||
diam voluptua. At
|
||
vero eos et
|
||
accusam et justo
|
||
duo dolores et ea
|
||
rebum. Stet clita
|
||
kasd gubergren,
|
||
no sea takimata
|
||
sanctus est Lorem
|
||
ipsum dolor sit
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||
amet.
|
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```
|
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|
||
*Find the exact string '(Lorem|dolor)' in example.txt*
|
||
```bash
|
||
fgrep '(Lorem|dolor)' example.txt
|
||
or
|
||
grep -F '(Lorem|dolor)' example.txt
|
||
```
|
||
```bash
|
||
foo (Lorem|dolor)
|
||
```
|
||
|
||
### f. `fmt`
|
||
Simple optimal text formatter
|
||
|
||
*Пример: example.txt (1 line)*
|
||
```bash
|
||
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
|
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```
|
||
|
||
*output the lines of example.txt to 20 character width*
|
||
```bash
|
||
cat example.txt | fmt -w 20
|
||
```
|
||
```bash
|
||
Lorem ipsum
|
||
dolor sit amet,
|
||
consetetur
|
||
sadipscing elitr,
|
||
sed diam nonumy
|
||
eirmod tempor
|
||
invidunt ut labore
|
||
et dolore magna
|
||
aliquyam erat, sed
|
||
diam voluptua. At
|
||
vero eos et
|
||
accusam et justo
|
||
duo dolores et ea
|
||
rebum. Stet clita
|
||
kasd gubergren,
|
||
no sea takimata
|
||
sanctus est Lorem
|
||
ipsum dolor sit
|
||
amet.
|
||
```
|
||
|
||
### g. `grep`
|
||
Looks for text inside files. You can use grep to search for lines of text that match one or many regular expressions, and outputs only the matching lines.
|
||
```bash
|
||
grep pattern filename
|
||
```
|
||
Пример:
|
||
```bash
|
||
$ grep admin /etc/passwd
|
||
_kadmin_admin:*:218:-2:Kerberos Admin Service:/var/empty:/usr/bin/false
|
||
_kadmin_changepw:*:219:-2:Kerberos Change Password Service:/var/empty:/usr/bin/false
|
||
_krb_kadmin:*:231:-2:Open Directory Kerberos Admin Service:/var/empty:/usr/bin/false
|
||
```
|
||
You can also force grep to ignore word case by using `-i` option. `-r` can be used to search all files under the specified directory, for Пример:
|
||
```bash
|
||
$ grep -r admin /etc/
|
||
```
|
||
And `-w` to search for words only. For more detail on `grep`, check following [link](https://www.cyberciti.biz/faq/grep-in-bash).
|
||
|
||
### h. `nl`
|
||
Number lines of files
|
||
|
||
*example.txt*
|
||
```bash
|
||
Lorem ipsum
|
||
dolor sit amet,
|
||
consetetur
|
||
sadipscing elitr,
|
||
sed diam nonumy
|
||
eirmod tempor
|
||
invidunt ut labore
|
||
et dolore magna
|
||
aliquyam erat, sed
|
||
diam voluptua. At
|
||
vero eos et
|
||
accusam et justo
|
||
duo dolores et ea
|
||
rebum. Stet clita
|
||
kasd gubergren,
|
||
no sea takimata
|
||
sanctus est Lorem
|
||
ipsum dolor sit
|
||
amet.
|
||
```
|
||
|
||
*show example.txt with line numbers*
|
||
```bash
|
||
nl -s". " example.txt
|
||
```
|
||
```bash
|
||
1. Lorem ipsum
|
||
2. dolor sit amet,
|
||
3. consetetur
|
||
4. sadipscing elitr,
|
||
5. sed diam nonumy
|
||
6. eirmod tempor
|
||
7. invidunt ut labore
|
||
8. et dolore magna
|
||
9. aliquyam erat, sed
|
||
10. diam voluptua. At
|
||
11. vero eos et
|
||
12. accusam et justo
|
||
13. duo dolores et ea
|
||
14. rebum. Stet clita
|
||
15. kasd gubergren,
|
||
16. no sea takimata
|
||
17. sanctus est Lorem
|
||
18. ipsum dolor sit
|
||
19. amet.
|
||
```
|
||
|
||
### i. `sed`
|
||
Stream editor for filtering and transforming text
|
||
|
||
*example.txt*
|
||
```bash
|
||
Hello This is a Test 1 2 3 4
|
||
```
|
||
|
||
*replace all spaces with hyphens*
|
||
```bash
|
||
sed 's/ /-/g' example.txt
|
||
```
|
||
```bash
|
||
Hello-This-is-a-Test-1-2-3-4
|
||
```
|
||
|
||
*replace all digits with "d"*
|
||
```bash
|
||
sed 's/[0-9]/d/g' example.txt
|
||
```
|
||
```bash
|
||
Hello This is a Test d d d d
|
||
```
|
||
|
||
### j. `sort`
|
||
Sort lines of text files
|
||
|
||
*example.txt*
|
||
```bash
|
||
f
|
||
b
|
||
c
|
||
g
|
||
a
|
||
e
|
||
d
|
||
```
|
||
|
||
*sort example.txt*
|
||
```bash
|
||
sort example.txt
|
||
```
|
||
```bash
|
||
a
|
||
b
|
||
c
|
||
d
|
||
e
|
||
f
|
||
g
|
||
```
|
||
|
||
*randomize a sorted example.txt*
|
||
```bash
|
||
sort example.txt | sort -R
|
||
```
|
||
```bash
|
||
b
|
||
f
|
||
a
|
||
c
|
||
d
|
||
g
|
||
e
|
||
```
|
||
|
||
### k. `tr`
|
||
Translate or delete characters
|
||
|
||
*example.txt*
|
||
```bash
|
||
Hello World Foo Bar Baz!
|
||
```
|
||
|
||
*take all lower case letters and make them upper case*
|
||
```bash
|
||
cat example.txt | tr 'a-z' 'A-Z'
|
||
```
|
||
```bash
|
||
HELLO WORLD FOO BAR BAZ!
|
||
```
|
||
|
||
*take all spaces and make them into newlines*
|
||
```bash
|
||
cat example.txt | tr ' ' '\n'
|
||
```
|
||
```bash
|
||
Hello
|
||
World
|
||
Foo
|
||
Bar
|
||
Baz!
|
||
```
|
||
|
||
### l. `uniq`
|
||
Report or omit repeated lines
|
||
|
||
*example.txt*
|
||
```bash
|
||
a
|
||
a
|
||
b
|
||
a
|
||
b
|
||
c
|
||
d
|
||
c
|
||
```
|
||
|
||
*show only unique lines of example.txt (first you need to sort it, otherwise it won't see the overlap)*
|
||
```bash
|
||
sort example.txt | uniq
|
||
```
|
||
```bash
|
||
a
|
||
b
|
||
c
|
||
d
|
||
```
|
||
|
||
*show the unique items for each line, and tell me how many instances it found*
|
||
```bash
|
||
sort example.txt | uniq -c
|
||
```
|
||
```bash
|
||
3 a
|
||
2 b
|
||
2 c
|
||
1 d
|
||
```
|
||
|
||
### m. `wc`
|
||
Tells you how many lines, words and characters there are in a file.
|
||
```bash
|
||
wc filename
|
||
```
|
||
Пример:
|
||
```bash
|
||
$ wc demo.txt
|
||
7459 15915 398400 demo.txt
|
||
```
|
||
Where `7459` is lines, `15915` is words and `398400` is characters.
|
||
|
||
## 1.3. Directory Operations
|
||
|
||
<table>
|
||
<tr>
|
||
<td><a href="#a-cd">cd</a></td>
|
||
<td><a href="#b-mkdir">mkdir</a></td>
|
||
<td><a href="#c-pwd">pwd</a></td>
|
||
</tr>
|
||
</table>
|
||
|
||
### a. `cd`
|
||
Moves you from one directory to other. Running this
|
||
```bash
|
||
$ cd
|
||
```
|
||
moves you to home directory. This command accepts an optional `dirname`, which moves you to that directory.
|
||
```bash
|
||
cd dirname
|
||
```
|
||
|
||
### b. `mkdir`
|
||
Makes a new directory.
|
||
```bash
|
||
mkdir dirname
|
||
```
|
||
|
||
### c. `pwd`
|
||
Tells you which directory you currently are in.
|
||
```bash
|
||
pwd
|
||
```
|
||
|
||
## 1.4. SSH, System Info & Network Operations
|
||
|
||
<table>
|
||
<tr>
|
||
<td><a href="#a-bg">bg</a></td>
|
||
<td><a href="#b-cal">cal</a></td>
|
||
<td><a href="#c-date">date</a></td>
|
||
<td><a href="#d-df">df</a></td>
|
||
<td><a href="#e-dig">dig</a></td>
|
||
<td><a href="#f-du">du</a></td>
|
||
<td><a href="#g-fg">fg</a></td>
|
||
<td><a href="#h-finger">finger</a></td>
|
||
<td><a href="#i-jobs">jobs</a></td>
|
||
<td><a href="#j-last">last</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td><a href="#k-man">man</a></td>
|
||
<td><a href="#l-passwd">passwd</a></td>
|
||
<td><a href="#m-ping">ping</a></td>
|
||
<td><a href="#n-ps">ps</a></td>
|
||
<td><a href="#o-quota">quota</a></td>
|
||
<td><a href="#p-scp">scp</a></td>
|
||
<td><a href="#q-ssh">ssh</a></td>
|
||
<td><a href="#r-top">top</a></td>
|
||
<td><a href="#s-uname">uname</a></td>
|
||
<td><a href="#t-uptime">uptime</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td><a href="#u-w">w</a></td>
|
||
<td><a href="#v-wget">wget</a></td>
|
||
<td><a href="#w-whoami">whoami</a></td>
|
||
<td><a href="#x-whois">whois</a></td>
|
||
</tr>
|
||
</table>
|
||
|
||
### a. `bg`
|
||
Lists stopped or background jobs; resume a stopped job in the background.
|
||
|
||
### b. `cal`
|
||
Shows the month's calendar.
|
||
|
||
### c. `date`
|
||
Shows the current date and time.
|
||
|
||
### d. `df`
|
||
Shows disk usage.
|
||
|
||
### e. `dig`
|
||
Gets DNS information for domain.
|
||
```bash
|
||
dig domain
|
||
```
|
||
|
||
### f. `du`
|
||
Shows the disk usage of files or directories. For more information on this command check this [link](http://www.linfo.org/du.html)
|
||
```bash
|
||
du [option] [filename|directory]
|
||
```
|
||
Options:
|
||
- `-h` (human readable) Displays output it in kilobytes (K), megabytes (M) and gigabytes (G).
|
||
- `-s` (supress or summarize) Outputs total disk space of a directory and supresses reports for subdirectories.
|
||
|
||
Пример:
|
||
```bash
|
||
du -sh pictures
|
||
1.4M pictures
|
||
```
|
||
|
||
### g. `fg`
|
||
Brings the most recent job in the foreground.
|
||
|
||
### h. `finger`
|
||
Displays information about user.
|
||
```bash
|
||
finger username
|
||
```
|
||
### i. `jobs`
|
||
Lists the jobs running in the background, giving the job number.
|
||
|
||
### j. `last`
|
||
Lists your last logins of specified user.
|
||
```bash
|
||
last yourUsername
|
||
```
|
||
|
||
### k. `man`
|
||
Shows the manual for specified command.
|
||
```bash
|
||
man command
|
||
```
|
||
|
||
### l. `passwd`
|
||
Allows the current logged user to change their password.
|
||
|
||
### m. `ping`
|
||
Pings host and outputs results.
|
||
```bash
|
||
ping host
|
||
```
|
||
|
||
### n. `ps`
|
||
Lists your processes.
|
||
```bash
|
||
ps -u yourusername
|
||
```
|
||
Use the flags ef. e for every process and f for full listing.
|
||
```bash
|
||
ps -ef
|
||
```
|
||
|
||
### o. `quota`
|
||
Shows what your disk quota is.
|
||
```bash
|
||
quota -v
|
||
```
|
||
|
||
### p. `scp`
|
||
Transfer files between a local host and a remote host or between two remote hosts.
|
||
|
||
*copy from local host to remote host*
|
||
```bash
|
||
scp source_file user@host:directory/target_file
|
||
```
|
||
*copy from remote host to local host*
|
||
```bash
|
||
scp user@host:directory/source_file target_file
|
||
scp -r user@host:directory/source_folder target_folder
|
||
```
|
||
This command also accepts an option `-P` that can be used to connect to specific port.
|
||
```bash
|
||
scp -P port user@host:directory/source_file target_file
|
||
```
|
||
|
||
### q. `ssh`
|
||
ssh (SSH client) is a program for logging into and executing commands on a remote machine.
|
||
```bash
|
||
ssh user@host
|
||
```
|
||
This command also accepts an option `-p` that can be used to connect to specific port.
|
||
```bash
|
||
ssh -p port user@host
|
||
```
|
||
|
||
### r. `top`
|
||
Displays your currently active processes.
|
||
|
||
### s. `uname`
|
||
Shows kernel information.
|
||
```bash
|
||
uname -a
|
||
```
|
||
|
||
### t. `uptime`
|
||
Shows current uptime.
|
||
|
||
### u. `w`
|
||
Displays who is online.
|
||
|
||
### v. `wget`
|
||
Downloads file.
|
||
```bash
|
||
wget file
|
||
```
|
||
|
||
### w. `whoami`
|
||
Return current logged in username.
|
||
|
||
### x. `whois`
|
||
Gets whois information for domain.
|
||
```bash
|
||
whois domain
|
||
```
|
||
|
||
## 1.5. Process Monitoring Operations
|
||
|
||
<table>
|
||
<tr>
|
||
<td><a href="#a-kill">kill</a></td>
|
||
<td><a href="#b-killall">killall</a></td>
|
||
<td><a href="#c-&">&</a></td>
|
||
<td><a href="#d-nohup">nohup</a></td>
|
||
</tr>
|
||
</table>
|
||
|
||
### a. `kill`
|
||
Kills (ends) the processes with the ID you gave.
|
||
```bash
|
||
kill PID
|
||
```
|
||
|
||
### b. `killall`
|
||
Kill all processes with the name.
|
||
```bash
|
||
killall processname
|
||
```
|
||
|
||
### c. &
|
||
The `&` symbol instructs the command to run as a background process in a subshell.
|
||
```bash
|
||
command &
|
||
```
|
||
|
||
### d. `nohup`
|
||
nohup stands for "No Hang Up". This allows to run command/process or shell script that can continue running in the background after you log out from a shell.
|
||
```bash
|
||
nohup command
|
||
```
|
||
Combine it with `&` to create background processes
|
||
```bash
|
||
nohup command &
|
||
```
|
||
|
||
# 2. Basic Shell Programming
|
||
|
||
|
||
The first line that you will write in bash script files is called `shebang`. This line in any script determines the script's ability to be executed like a standalone executable without typing sh, bash, python, php etc beforehand in the terminal.
|
||
|
||
```bash
|
||
#!/usr/bin/env bash
|
||
```
|
||
|
||
## 2.1. Variables
|
||
|
||
Creating variables in bash is similar to other languages. There are no data types. A variable in bash can contain a number, a character, a string of characters, etc. You have no need to declare a variable, just assigning a value to its reference will create it.
|
||
|
||
Пример:
|
||
```bash
|
||
str="hello world"
|
||
```
|
||
|
||
The above line creates a variable `str` and assigns "hello world" to it. The value of variable is retrieved by putting the `$` in the beginning of variable name.
|
||
|
||
Пример:
|
||
```bash
|
||
echo $str # hello world
|
||
```
|
||
## 2.2. Array
|
||
Like other languages bash has also arrays. An array is variable containing multiple values. There's no maximum limit on the size of array. Array in bash are zero based. The first element is indexed with element 0. There are several ways for creating arrays in bash. Which are given below.
|
||
|
||
Examples:
|
||
```bash
|
||
array[0] = val
|
||
array[1] = val
|
||
array[2] = val
|
||
array=([2]=val [0]=val [1]=val)
|
||
array=(val val val)
|
||
```
|
||
To display a value at specific index use following syntax:
|
||
|
||
```bash
|
||
${array[i]} # where i is the index
|
||
```
|
||
|
||
If no index is supplied, array element 0 is assumed. To find out how many values there are in the array use the following syntax:
|
||
|
||
```bash
|
||
${#array[@]}
|
||
```
|
||
|
||
Bash has also support for the ternary conditions. Check some examples below.
|
||
|
||
```bash
|
||
${varname:-word} # if varname exists and isn't null, return its value; otherwise return word
|
||
${varname:=word} # if varname exists and isn't null, return its value; otherwise set it word and then return its value
|
||
${varname:+word} # if varname exists and isn't null, return word; otherwise return null
|
||
${varname:offset:length} # performs substring expansion. It returns the substring of $varname starting at offset and up to length characters
|
||
```
|
||
|
||
## 2.3 String Substitution
|
||
|
||
Check some of the syntax on how to manipulate strings
|
||
|
||
```bash
|
||
${variable#pattern} # if the pattern matches the beginning of the variable's value, delete the shortest part that matches and return the rest
|
||
${variable##pattern} # if the pattern matches the beginning of the variable's value, delete the longest part that matches and return the rest
|
||
${variable%pattern} # if the pattern matches the end of the variable's value, delete the shortest part that matches and return the rest
|
||
${variable%%pattern} # if the pattern matches the end of the variable's value, delete the longest part that matches and return the rest
|
||
${variable/pattern/string} # the longest match to pattern in variable is replaced by string. Only the first match is replaced
|
||
${variable//pattern/string} # the longest match to pattern in variable is replaced by string. All matches are replaced
|
||
${#varname} # returns the length of the value of the variable as a character string
|
||
```
|
||
|
||
## 2.4. Functions
|
||
As in almost any programming language, you can use functions to group pieces of code in a more logical way or practice the divine art of recursion. Declaring a function is just a matter of writing function my_func { my_code }. Calling a function is just like calling another program, you just write its name.
|
||
|
||
```bash
|
||
function name() {
|
||
shell commands
|
||
}
|
||
```
|
||
|
||
Пример:
|
||
```bash
|
||
#!/bin/bash
|
||
function hello {
|
||
echo world!
|
||
}
|
||
hello
|
||
|
||
function say {
|
||
echo $1
|
||
}
|
||
say "hello world!"
|
||
```
|
||
|
||
When you run the above example the `hello` function will output "world!". The above two functions `hello` and `say` are identical. The main difference is function `say`. This function, prints the first argument it receives. Arguments, within functions, are treated in the same manner as arguments given to the script.
|
||
|
||
## 2.5. Conditionals
|
||
|
||
The conditional statement in bash is similar to other programming languages. Conditions have many form like the most basic form is `if` expression `then` statement where statement is only executed if expression is true.
|
||
|
||
```bash
|
||
if [ expression ]; then
|
||
will execute only if expression is true
|
||
else
|
||
will execute if expression is false
|
||
fi
|
||
```
|
||
|
||
Sometime if conditions becoming confusing so you can write the same condition using the `case statements`.
|
||
|
||
```bash
|
||
case expression in
|
||
pattern1 )
|
||
statements ;;
|
||
pattern2 )
|
||
statements ;;
|
||
...
|
||
esac
|
||
```
|
||
|
||
Expression Examples:
|
||
|
||
```bash
|
||
statement1 && statement2 # both statements are true
|
||
statement1 || statement2 # at least one of the statements is true
|
||
|
||
str1=str2 # str1 matches str2
|
||
str1!=str2 # str1 does not match str2
|
||
str1<str2 # str1 is less than str2
|
||
str1>str2 # str1 is greater than str2
|
||
-n str1 # str1 is not null (has length greater than 0)
|
||
-z str1 # str1 is null (has length 0)
|
||
|
||
-a file # file exists
|
||
-d file # file exists and is a directory
|
||
-e file # file exists; same -a
|
||
-f file # file exists and is a regular file (i.e., not a directory or other special type of file)
|
||
-r file # you have read permission
|
||
-s file # file exists and is not empty
|
||
-w file # you have write permission
|
||
-x file # you have execute permission on file, or directory search permission if it is a directory
|
||
-N file # file was modified since it was last read
|
||
-O file # you own file
|
||
-G file # file's group ID matches yours (or one of yours, if you are in multiple groups)
|
||
|
||
file1 -nt file2 # file1 is newer than file2
|
||
file1 -ot file2 # file1 is older than file2
|
||
|
||
-lt # less than
|
||
-le # less than or equal
|
||
-eq # equal
|
||
-ge # greater than or equal
|
||
-gt # greater than
|
||
-ne # not equal
|
||
```
|
||
|
||
## 2.6. Loops
|
||
|
||
There are three types of loops in bash. `for`, `while` and `until`.
|
||
|
||
Different `for` Syntax:
|
||
```bash
|
||
for x := 1 to 10 do
|
||
begin
|
||
statements
|
||
end
|
||
|
||
for name [in list]
|
||
do
|
||
statements that can use $name
|
||
done
|
||
|
||
for (( initialisation ; ending condition ; update ))
|
||
do
|
||
statements...
|
||
done
|
||
```
|
||
|
||
`while` Syntax:
|
||
```bash
|
||
while condition; do
|
||
statements
|
||
done
|
||
```
|
||
|
||
`until` Syntax:
|
||
```bash
|
||
until condition; do
|
||
statements
|
||
done
|
||
```
|
||
|
||
# 3. Tricks
|
||
|
||
## Set an alias
|
||
Open `bash_profile` by running following command `nano ~/.bash_profile`
|
||
> alias dockerlogin='ssh www-data@adnan.local -p2222' # add your alias in .bash_profile
|
||
|
||
## To quickly go to a specific directory
|
||
nano ~/.bashrc
|
||
> export hotellogs="/workspace/hotel-api/storage/logs"
|
||
|
||
```bash
|
||
source ~/.bashrc
|
||
cd $hotellogs
|
||
```
|
||
|
||
## Exit traps
|
||
|
||
Make your bash scripts more robust by reliably performing cleanup.
|
||
|
||
```bash
|
||
function finish {
|
||
# your cleanup here. e.g. kill any forked processes
|
||
jobs -p | xargs kill
|
||
}
|
||
trap finish EXIT
|
||
```
|
||
|
||
## Saving your environment variables
|
||
|
||
When you do `export FOO = BAR`, your variable is only exported in this current shell and all its children, to persist in the future you can simply append in your `~/.bash_profile` file the command to export your variable
|
||
```bash
|
||
echo export FOO=BAR >> ~/.bash_profile
|
||
```
|
||
|
||
## Accessing your scripts
|
||
|
||
You can easily access your scripts by creating a bin folder in your home with `mkdir ~/bin`, now all the scripts you put in this folder you can access in any directory.
|
||
|
||
If you can not access, try append the code below in your `~/.bash_profile` file and after do `source ~/.bash_profile`.
|
||
```bash
|
||
# set PATH so it includes user's private bin if it exists
|
||
if [ -d "$HOME/bin" ] ; then
|
||
PATH="$HOME/bin:$PATH"
|
||
fi
|
||
```
|
||
|
||
# 4. Debugging
|
||
You can easily debug the bash script by passing different options to `bash` command. For example `-n` will not run commands and check for syntax errors only. `-v` echo commands before running them. `-x` echo commands after command-line processing.
|
||
|
||
```bash
|
||
bash -n scriptname
|
||
bash -v scriptname
|
||
bash -x scriptname
|
||
```
|
||
|
||
## Contribution
|
||
|
||
- Report issues [How to](https://help.github.com/articles/creating-an-issue/)
|
||
- Open pull request with improvements [How to](https://help.github.com/articles/about-pull-requests/)
|
||
- Spread the word
|
||
|
||
## Translation
|
||
- [Chinese | 简体中文](https://github.com/vuuihc/bash-guide)
|
||
- [Turkish | Türkçe](https://github.com/omergulen/bash-guide)
|
||
- [Japanese | 日本語](https://github.com/itooww/bash-guide)
|
||
|
||
## License
|
||
|
||
[](https://creativecommons.org/licenses/by/4.0/)
|