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This article mainly shows you "what are the Linux file commands", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn "what are the Linux file commands" this article.

Files and commands

In the Linux/UNIX operating system, everything is treated as files: hardware devices (including keyboards and terminals), directories, commands themselves, and, of course, files. This strange convention is actually the basis of Linux/UNIX 's ability and flexibility.

Most (almost all) commands are in the following form:

Command [option] [source file (s)] [target file]

Get help

One of the most useful commands is those that help (especially for those who learn Linux). Two important sources of information in Linux are the online reference manual, or man pages and whatis tools. You can use the whatis command to access the man page of an unfamiliar command.

To learn more about this command, ◆ whatis echo can use:

◆ manecho if you don't know the commands required for a particular task, you can use man-k (also known as apropos) and a topic to generate possible commands. For example:

◆ man-k files a useful but often overlooked command provides information about using man itself:

◆ man man you can use SPACEBAR to browse any man page; UP ARROW will scroll the file up. . To exit, enter Q _ department, or CTRL-Z.

User category

Remember the famous saying, "all animals are equal, but some animals are more equal than others"? In the Linux world, the root user is in charge.

The root user can log in with another user name, su (derived from "superuser"). To perform tasks such as adding a new user, printer, or file system, you must log in as a root user or switch to the root user with the su command and root password. System files, including system files that control the initialization process, are owned by the root user. Although ordinary users may be allowed to read them, for system security reasons, editing rights will be left to the root user.

BASH shell

Although other shell is provided, BASH (Bourne Again Shell) is the default shell for Linux. It combines the features of Bourne shell of the same name with the features of Korn, C, and TCSH shell.

The built-in command in BASH history records 500 commands entered by default. You can view them by entering history at the command prompt. To retrieve a particular command, press UP ARROW or DOWN ARROW at the command prompt, or enter its number in the history list and precede it with "!". You can also execute the command through the distance from the top item in the history list: if there are 53 events in the history list, $!-3 will execute the event number 51. Like other shell in the UNIX/Linux world, BASH uses special environment variables to facilitate system administration. For example:

◆ HOME, user home directory

The search path used by ◆ PATH,Linux to search for the executable image of the command you entered

◆ HISTSIZE, the number of historical events saved by the system

In addition to these reserved keywords, you can also define your own environment variables. For example, Oracle uses ORACLE_HOME (and other variables) that must be set in your environment for the Oracle installation to complete successfully. Alternatively, make system-wide * * settings in / etc/profile (root privileges are required) or local * * settings in .profile. You can view the value of an environment variable by accessing it through the echo command with a $symbol. You can use the env command to view all current environment variables.

Regular expressions and wildcards

Many Linux file commands use wildcards? To match any number of characters or any single character respectively; regular pattern matching expressions use a period (.) To match any single character except the newline character. In both cases, square brackets ([]) are used to match character groups other than the "*" sign. However, the number has a similar but different meaning in various cases: although it will match one or more characters in shell, it matches zero or more instances of these characters in regular expressions. Some commands, such as egrep and awk, use a broader set of special characters for pattern matching.

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