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This article mainly shows you the "Linux entry must learn what the document processing commands are", 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 "Linux entry must learn what document processing commands have" this article.

Linux system information is stored in files, which are similar to ordinary official documents. Each file has its own name, content, storage address and other management information, such as the user of the file, the size of the file, and so on. The file can be a letter, an address book, or the source statement of the program, the data of the program, or even the executable program and other non-text content. Linux file system has a good structure, the system provides a lot of file processing programs. This paper mainly introduces the commonly used file processing commands.

File

1. Action

File determines the file type by probing the contents of the file, and the permission is for all users.

two。 Format

File

[options] File name

3. [options] main parameters

-v: displays version information after standard output and exits.

-z: detects compressed file types.

-L: allow matching connections.

-f

Name: reads the list of file names to analyze from the file namefile.

4. Simple explanation

Using the file command, you can know whether a file is a binary (ELF format) executable, an Shell Script file, or some other format. The file types that file can recognize are directories, Shell scripts, English text, binary executable files, C language source files, text files, and DOS executable files.

5. Application example

If we see a file grap without a suffix, we can use the following command:

$file grap

Grap:English text

At this point, the system shows that this is an English text file. It is important to note that the file command cannot detect multimedia file types, including graphics, audio, video, and so on.

Mkdir

1. Action

The purpose of the mkdir command is to create a subdirectory named dirname, which is similar to the md command under MS DOS and has permissions for all users.

two。 Format

Mkdir

[options] directory name

3. [options] main parameters

-mmam Murray Mode= mode: set permissions; similar to chmod.

-pmam music: create an upper-level directory if necessary; if the directory already exists, it will not be regarded as an error.

-vmam Meltel verbose: every time a new directory is created, information is displayed.

-- version: leave after the version information is displayed.

4. Application example

The permissions of the directory can be set when creating the directory, and the parameter used in this case is "- m". Assuming that the directory name you want to create is "tsk" so that all users have rwx (that is, read, write, and execute permissions), you can use the following command:

$mkdir-m 777 tsk

Grep

1. Action

The grep command can specify that specific content be searched in the file and standard output the lines containing that content. The full name of grep is Global Regular Expression Print, which represents the global regular expression version, and its permission is for all users.

two。 Format

Grep [options]

3. Main parameters

[options] main parameters:

-c: outputs only the count of matching rows.

-I: case-insensitive (for single characters only).

-h: the file name is not displayed when querying multiple files.

-l: when querying multiple files, only the file names that contain matching characters are output.

-n: displays matching lines and line numbers.

-s: does not display error messages that do not exist or have no matching text.

-v: displays all lines that do not contain matching text.

The main parameters of the pattern regular expression:

\: ignore the original meaning of special characters in regular expressions.

^: matches the start line of the regular expression.

$: matches the end line of the regular expression.

\;: to the end of the line matching the regular expression.

[

]: a single character, such as [A] that is, A meets the requirements.

[

-]: range, such as [Amurz], that is, A, B, C all the way up to Z all meet the requirements.

. All single characters

*: there are characters, and the length can be 0.

Regular expression is a very important concept in Linux/Unix system. A regular expression (also known as "regex" or "regexp") is a Pattern that can describe a class of strings. If a string can be described by a regular expression, we say that the character matches the regular expression (Match). This is similar to the fact that users in DOS can use the wildcard "*" to represent any character. On Linux systems, regular expressions are often used to find patterns for text, as well as to perform search-and-replace operations and other functions on text.

4. Application example

Querying DNS services is one of the daily tasks, which means maintaining a large number of IP addresses covering different networks. Sometimes there are more than 2000 IP addresses. If you want to look at the nnn.nnn network address, but forget the rest of the second part, you only know that there are two periods, such as nnn nn... To extract all of these nnn.nnn IP addresses, use [0-9]\ {3\}\. [0-0\ {3\}\. The meaning is that any number appears three times, followed by a period, followed by a period.

$grep

'[0-9]\ {3\}. [0-0\ {3\}\' ipfile

In addition, the grep family also includes fgrep and egrep. Fgrep is a fix grep that allows you to find strings rather than a pattern; egrep is an extended grep that supports basic and extended regular expressions, but does not support the application of the\ Q pattern range and some of the more standardized patterns corresponding to it.

Dd

1. Action

The dd command is used to copy files and convert and format data based on parameters.

two。 Format

Dd [options]

3. [opitions] main parameters

Bs= bytes: force ibs=; and obs=;.

Cbs= bytes: specified for each conversion;.

Conv= keyword: converts files based on how they are represented by comma-delimited keywords.

Number of count= blocks: only the input data of the specified; is copied.

Ibs= bytes: read the specified; each time.

If= file: read; content, not standard input data.

Obs= bytes: each time you write the specified;.

Of= file: writes data to;, instead of displaying it in standard output.

Number of seek= blocks: the output data of the specified; in obs units is skipped first.

Number of skip= blocks: skip the input data specified in ibs; first.

4. Application example

The dd command is often used to make a Linux boot disk. Find a bootable kernel so that its root device points to the correct root partition, and then use the dd command to write it to the floppy disk:

$rdev vmlinuz / dev/hda $dd if=vmlinuz of=/dev/fd0

The above code shows that using the rdev command to point the root device in the bootable kernel vmlinuz to / dev/hda, please replace "hda" with your own root partition, and then use the dd command to write the kernel to the floppy disk.

Find

1. Action

The function of the find command is to search for files in the directory, and its permission is for all users.

two。 Format

Find [path] [options] [expression]

Path specifies the directory path, from which the system starts looking down the directory tree for files. It is a list of paths separated from each other by spaces. If you do not write path, it defaults to the current directory.

3. Main parameters

[options] parameters:

-depth: use the depth-level search process to find the contents of files first in a specified directory at a certain layer.

-maxdepth levels: indicates that at most the level subdirectory of the start directory can be found. Level is a non-negative number, and if level is 0, it means to look only in the current directory.

-mindepth levels: indicates that at least the level subdirectory of the start directory is found.

-mount: do not look in directories and files of other file systems (such as Msdos, Vfat, etc.).

-version: printed version.

[expression] is a matching expression, an expression accepted by the find command, and all operations of the find command are directed against the expression. It has a lot of parameters, and only some commonly used parameters are introduced here.

-name: wildcard characters * and? are supported.

-atime n: search for files that have been read in the past n days.

-ctime n: search for files that have been modified in the past n days.

-group grpoupname: search for all files whose group is grpoupname.

-user user name: search for all files that belong to a user name (ID or name).

-size n: search for files whose file size is n block.

-print: output the search results and print them.

4. Application skills

There are several ways for the find command to find files:

(1) search based on file name

For example, if we want to find a file with the file name lilo.conf, we can use the following command:

Find /-name lilo.conf

The "/" after the find command means to search the entire hard disk.

(2) quickly find files

A real problem with finding files by file name is that it takes quite a long time, especially when large Linux file systems and large hard disk files are placed in deep subdirectories. If we know that the file is stored in a directory, we can save a lot of time just looking down in that directory. For example, the smb.conf file, which can be judged to be a configuration file by its file suffix ".conf", should be in the / etc directory, where you can use the following command:

Find / etc-name smb.conf

In this way, you can shorten the time by using the Quick find File method.

(3) search method according to some file names

Sometimes we know that only one file contains the word abvd, so to find all the files in the system that contain these four characters, enter the following command:

Find /-name'* abvd*'

After entering this command, the Linux system will look in the / directory for all files containing the four characters of abvd (where * is a wildcard), such as abvdrmyz and other eligible files can be displayed.

(4) use hybrid search method to find files.

The find command can use a hybrid lookup method. For example, if we want to find a file in the / etc directory that is larger than 500000 bytes and is modified within 24 hours, we can use-and (and) to link the two lookup parameters together to form a hybrid lookup.

Find / etc-size + 500000c-and-mtime + 1

Mv

1. Action

The mv command is used to rename a file or directory, or to move a file from one directory to another, with permissions for all users. This command is like a combination of ren and move in the DOS command.

two。 Format

Mv [options] Source file or directory destination file or directory

3. [options] main parameters

-I: operate interactively. If the mv operation will result in an overwrite of an existing target file, the system asks whether to rewrite and asks the user to answer "y" or "n" to avoid mistakenly overwriting the file.

-f: interoperability is prohibited. The mv operation does not give any indication when it wants to overwrite an existing target file, and the I parameter will no longer work when this parameter is specified.

4. Application example

(1) move all files in / usr/cbu to the current directory (with "." Represents):

$mv / usr/cbu/ *.

(2) rename the file cjh.txt to wjz.txt:

$mv cjh.txt wjz.txt

Ls

1. Action

The ls command is used to display the contents of the directory, similar to the dir command under DOS, with permissions for all users.

two。 Format

Ls [options] [filename]

Main parameters of 3.options

-a mathmum Murall: do not hide anything to "." The item at the beginning of the character.

List any items except ".." and "..".

-- author: print out the author of each document.

The octal overflow sequence represents non-printable characters.

-- block-size= size: the block is in bytes of the specified;.

No items ending with the ~ character are listed.

-f: no sorting,-aU parameter takes effect,-lst parameter is invalid.

-Fmam: add a file type indicator (* / = @ | one of them).

-g:like-l, but do

Not list owner .

-Gregory Mustang Mustang display of group information group is a group of people

-imam Murray Inode: list the inode number of each file.

-Imam color color = style: do not print any items that match the Shell universal character;.

-k: namely-- block-size=1K.

-l: lists information in a longer format.

When the file information of the symbolic link is displayed, the object indicated by the symbolic link is displayed instead of the information of the symbolic link itself.

-m: all items are separated by commas and fill the entire line width.

Similar to-l, but UID and GID numbers are listed.

-Nmam Mustel literal: lists unprocessed project names, such as no special handling of control characters.

-pmam: add an indication of the file type (/ = @ | one of them).

-Qmam quotation name: enclose the project name in double quotation marks.

-rmam Murray reverse: arranged in reverse order.

-Rmine Meltel recursive: lists all subdirectory layers at the same time.

-srecom Musi size: in order of block size.

4. Application example

The ls command is the most frequently used command in the Linux system, and its parameters are also the most frequently used in the Linux command. There are several different colors when using the ls command, including blue for directories, green for executable files, red for compressed files, light blue for linked files, bold black for symbolic links, and gray for other formats. Ls- l is most commonly used in ls

The file type begins with a string of 10 characters. Where * * characters represent the file type, which can be one of the following types:-(normal file), d (directory), l (symbolic link), b (block device file), c (character device file). The next nine characters represent the access to the file, divided into three groups, each with 3 bits. The * group indicates that the file belongs to the master, the second group represents the permissions of users in the same group, and the third group represents the permissions of other users. The three characters in each group represent read (r), write (w), and execute permissions (x) to the file, respectively. For directories, entry permissions. S means that when a file is executed, the UID or GID of the file is assigned to the UID (user ID) or GID (group ID) of the executing process. T means to set the flag bit (stay in memory and not be swapped out). If the file is a directory, the files in that directory can only be deleted by the superuser, the directory owner, or the file owner. If it is an executable file, the pointer to its body segment remains in memory after the file is executed. This way, when it is executed again, the system can load the file more quickly. This is followed by the file size, generation time, file or command name.

Diff

1. Action

The diff command is used to compare two files and points out that the difference between the two is that it has permissions for all users.

two。 Format

Diff

[options] Source file target file

3. [options] main parameters

-a: treat all files as text files.

-b: the difference caused by ignoring spaces.

-B: the difference caused by ignoring blank lines.

-c: use the outline output format.

-H: use heuristics to speed up the search for large files.

-I: ignore case changes.

-n

-- rcs: output in RCS format.

Cmp

1. Action

The cmp (abbreviation for "compare") command is used to briefly indicate whether there is a difference between the two files, and its permission is for all users.

two。 Format

Cmp [options] file name

3. [options] main parameters

-l: output bytes in decimal mode, and facilitate the output of different files in octal mode.

Cat

1. Action

The cat (abbreviation for "concatenate") command is used to connect and display information about one or more specified files, and its permissions are for all users.

two。 Format

Cat

[options] File 1, document 2.

3. [options] main parameters

-n: number the number of lines of all output starting with the * line.

-b: similar to-n, except that blank lines are not numbered.

-s: when you encounter blank lines with more than two consecutive lines, replace them with blank lines on one line.

4. Application example

(1) one of the simplest uses of the cat command is to display the contents of a text file. For example, if we want to see the contents of the README file on the command line, we can use the command:

$cat README

(2) sometimes it is necessary to process several files into a single file and save the results of this processing to a separate output file. The cat command accepts one or more files on its input and prints them to its output as a separate file. For example, after numbering the contents of README and INSTALL files (no blank lines), append the contents to a new text file, File1:

$cat README INSTALL File1

(3) another important function of cat is the ability to number rows, as shown in figure 2. This function is convenient for the preparation of program documentation, as well as legal and scientific documentation, and the line number printed on the left makes it easy to reference a part of the document. these are very important in programming, scientific research, business reports and even legislative work.

Figure 2 numbering using the cat command / etc/named.conf file

The line numbering function has two parameters:-b (only non-blank lines can be numbered) and-n (all lines can be numbered):

$cat-b / etc/named.conf

Ln

1. Action

The ln command is used to create links between files, and its permissions are for all users.

two。 Format

Ln

[options] Source file [link name]

3. Parameters.

-f: delete the source file when linking.

-d: allows system administrators to hard-link their own directories.

-s: soft link (Symbolic Link).

-b: back up files that will be overwritten or deleted when linked.

There are two kinds of links, one is called Hard Link, the other is called symbolic link (Symbolic Link). By default, the ln command produces hard links.

A hard connection is a connection made through an index node. In Linux's file system, files saved in disk partitions, regardless of type, are assigned a number called index node number (Inode Index). In Linux, it is possible to have multiple file names pointing to the same Inode. Generally speaking, this kind of connection is a hard connection. The purpose of a hard connection is to allow a file to have multiple valid pathnames, so that users can establish a hard connection to important files to prevent "accidental deletion". The reason is as mentioned above, because there is more than one connection to the index node of the directory. Deleting only one connection does not affect the Inode itself and other connections. Only when a connection is deleted will the connection of the file's data block and directory be released. In other words, the file will really be deleted.

Corresponding to the hard connection, there is another kind of connection in the Lnux system, which is called symbolic connection (Symbilc Link), also called soft connection. Soft-link files are a bit like Windows shortcuts. It is actually a kind of special file. In symbolic links, a file is actually a text file that contains information about the location of another file.

Practice

Above we introduced the Linux file processing commands, here are a few examples, you can start to practice the commands just mentioned.

1. Use symbolic links to quickly access key directories

Symbolic links are a very practical feature. Suppose there are some directories or files that need to be used frequently, but because of the file and directory structure of Linux, this file or directory is in a very deep subdirectory. For example, Apache

The Web server document is in the / usr/local/httpd/htdocs of the system, and you don't want to enter such a long path from the home directory every time (in fact, this path is also very difficult to remember).

To solve this problem, you can create a symbolic link in the home directory so that when you need to enter that directory, you only need to go to that link.

To easily access the directory where the Web server (/ usr/local/httpd/htdocs) documents are located, you can use the following command in the home directory:

$ln-s / usr/local/httpd/htdocs gg

In this way, every time you enter the gg directory, you can access the documents of the Web server. In the future, if you no longer access the documents of the Web server, you can delete the gg, but the documents of the real Web server are not deleted.

two。 Use the dd command to import root.ram content in init.rd format into memory

Dd if=/dev/fd0 of=floppy.fd

Dd if=root.ram of=/dev/ram0 #

3.grep command system call

Grep is one of the most widely used commands in Linux/Unix and can be called internally by many Linux systems.

(1) if you want to query the directories in the directory list, the method is as follows:

$ls-l | grep '∧ d'

(2) if you query all files that do not contain a directory in a directory, the method is as follows:

$ls-l | grep '∧ [∧ d]'

(3) call grep with the find command, such as "Chinput" in all C source code, as follows:

$find / ZhXwin-name *. C-exec grep-Q-s Chinput {}\;-print is all the contents of this article entitled "what are the file processing commands for getting started with Linux?" Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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