On Unix-like operating systems, the cat command reads data from files, and outputs their contents. It is the simplest way to display the contents of a file at the command line.
This document covers the GNU/Linux version of cat.
cat stands for "catenate." It is one of the most commonly-used commands in Unix-like operating systems. It can be used to:
Display text files
Copy text files into a new document
Append the contents of a text file to the end of another text file, combining them
Displaying text files
The simplest way to use cat is to give it the name of a text file. It displays the contents of the text file on the screen. For instance:
cat mytext.txt
...will read the contents of mytext.txt and send them to standard output (your terminal screen). If mytext.txt is very long, they will zoom past and you will only see the last screen's worth of your document.
If you want to view the document page-by-page or scroll back and forth through the document, you can use a pager or viewer such as pg, more, or less.
If you specify more than one file name, cat displays those files one after the other, catenating their contents to standard output. So this command:
cat mytext.txt mytext2.txt
Will print the contents of those two text files as if they were a single file.
Copy a text file
Normally you would copy a file with the cp command. You can use cat to make copies of text files in much the same way.
cat sends its output to stdout (standard output), which is usually the terminal screen. However, you can redirect this output to a file using the shell redirection symbol ">".
For instance, this command:
cat mytext.txt > newfile.txt
...will read the contents of mytext.txt and send them to standard output; instead of displaying the text, however, the shell will redirect the output to the file newfile.txt. If newfile.txt does not exist, it will be created. If newfile.txt already exists, it will be overwritten and its previous contents will be lost, so be careful.
Similarly, you can catenate several files into your destination file. For instance:
cat mytext.txt mytext2.txt > newfile.txt
...will read the contents of mytext.txt and mytext2.txt and write the combined text to the file newfile.txt. Again, if newfile.txt does not already exist, it will be created; if it already exists, it will be overwritten.
Append a text file's contents to another text file
Instead of overwriting another file, you can also append a source text file to another using the redirection operator ">>".
For instance:
cat mytext.txt >> another-text-file.txt
...will read the contents of mytext.txt, and write them at the end of another-text-file.txt. If another-text-file.txt does not already exist, it will be created and the contents of mytext.txt will be written to the new file.
The cat command also works for multiple text files as well:
...will write the combined contents of mytext.txt and mytext2.txt to the end of another-text-file.txt.
Incorporating standard input into cat output
cat reads from standard input if you specify a hyphen ("-") as a file name. For example, if you have a file, list.txt, which contains the following text:
apples
oranges
butter
bread
...you could use the echo command to output text, pipe that output to cat, and instruct cat to catenate it with the file's contents, like this:
echo "My Shopping List" | cat - list.txt
...which would output the following text:
My Shopping List
apples
oranges
butter
bread
In short, cat is a simple but very useful tool for working with the data in text files, system logs, configuration files, and any other human-readable data stored in a file.
These options are available on GNU cat, which is standard on most Linux distributions. If you are using a different Unix-like operating system (BSD, for example), some of these options may not be available; check your specific documentation for details.
-A, --show-all
Equivalent to -vET.
-b, --number-nonblank
Number non-empty output lines. This option overrides -n.
Read the contents of file.txt and display them on the screen.
cat file1.txt file2.txt
Reads the contents of file1.txt and file2.txt, and displays them in order on the terminal screen.
cat file.txt > newfile.txt
Read the contents of file.txt and write them to newfile.txt, overwriting anything newfile.txt previously contained. If newfile.txt does not exist, it will be created.
cat file.txt >> another-file.txt
Read the contents of file.txt and append them to the end of another-file.txt. If another-file.txt does not exist, it will be created.
cat -s file.txt
Display the contents of file.txt, omitting any repeated blank lines.
cat (命令行中顯示文件內容)
在類unix操作系統上，cat命令從文件中讀取數據，并輸出其內容。 這是在命令行中顯示文件內容的最簡單方法。 本文介紹了GNU/Linux版本的cat。
On Unix-like operating systems, the cat command reads data from files, and outputs their contents. It is the simplest way to display the contents of a file at the command line. This document covers the GNU/Linux version of cat.
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1 cat 運行系統環境
2 Description
3 Syntax
4 Options
5 Examples
cat 運行系統環境
Unix&Linux
Description
cat代表“ catenate”。它是類Unix操作系統中最常用的命令之一。它可以用于：
顯示文字檔
使用cat的最簡單方法是為其命名一個文本文件。它在屏幕上顯示文本文件的內容。例如：
...將讀取mytext.txt的內容并將其發送到標準輸出（您的終端屏幕）。如果mytext.txt太長，它們將縮放過去，并且您只會看到文檔最后一屏的價值。
如果要逐頁查看文檔或在文檔中來回滾動，可以使用尋呼機或查看器，例如pg，more或less。
如果您指定多個文件名，cat會依次顯示這些文件，并將其內容鏈接到標準輸出。所以這個命令：
將打印這兩個文本文件的內容，就像它們是單個文件一樣。
復制文本文件
通常，您將使用cp命令復制文件。您可以使用cat以幾乎相同的方式制作文本文件的副本。
cat將其輸出發送到stdout（標準輸出），通常是終端屏幕。但是，您可以使用外殼重定向符號“ > ” 將此輸出重定向到文件。
例如，此命令：
...將讀取mytext.txt的內容并將其發送到標準輸出；但是，外殼程序不顯示文本，而是將輸出重定向到文件newfile.txt。如果newfile.txt不存在，將創建它。如果newfile.txt已經存在，它將被覆蓋并且其先前的內容將丟失，因此請小心。
同樣，您可以將幾個文件分類到目標文件中。例如：
...將讀取mytext.txt和mytext2.txt的內容，并將合并的文本寫入文件newfile.txt中。同樣，如果newfile.txt不存在，將創建它；否則，將創建它。如果已經存在，它將被覆蓋。
將文本文件的內容附加到另一個文本文件
除了覆蓋另一個文件，您還可以使用重定向操作符“ >> ” 將源文本文件附加到另一個文件。
例如：
...將讀取mytext.txt的內容，并將其寫在another-text-file.txt的末尾。如果another-text-file.txt不存在，將創建該文件，并將mytext.txt的內容寫入新文件。
cat命令也適用于多個文本文件：
...將把mytext.txt和mytext2.txt的組合內容寫到another-text-file.txt的末尾。
將標準輸入合并到cat輸出中
如果您將連字符（“ - ”）指定為文件名，則cat將從標準輸入中讀取。例如，如果您有一個文件list.txt，其中包含以下文本：
...您可以使用echo命令輸出文本，將輸出通過管道傳遞給cat，并指示cat用文件的內容對其進行分類，如下所示：
...這將輸出以下文本：
簡而言之，cat是用于處理文本文件，系統日志，配置文件以及文件中存儲的任何其他可讀數據的數據的簡單但非常有用的工具。
cat stands for "catenate." It is one of the most commonly-used commands in Unix-like operating systems. It can be used to:
Displaying text files
The simplest way to use cat is to give it the name of a text file. It displays the contents of the text file on the screen. For instance:
...will read the contents of mytext.txt and send them to standard output (your terminal screen). If mytext.txt is very long, they will zoom past and you will only see the last screen's worth of your document.
If you want to view the document page-by-page or scroll back and forth through the document, you can use a pager or viewer such as pg, more, or less.
If you specify more than one file name, cat displays those files one after the other, catenating their contents to standard output. So this command:
Will print the contents of those two text files as if they were a single file.
Copy a text file
Normally you would copy a file with the cp command. You can use cat to make copies of text files in much the same way.
cat sends its output to stdout (standard output), which is usually the terminal screen. However, you can redirect this output to a file using the shell redirection symbol ">".
For instance, this command:
...will read the contents of mytext.txt and send them to standard output; instead of displaying the text, however, the shell will redirect the output to the file newfile.txt. If newfile.txt does not exist, it will be created. If newfile.txt already exists, it will be overwritten and its previous contents will be lost, so be careful.
Similarly, you can catenate several files into your destination file. For instance:
...will read the contents of mytext.txt and mytext2.txt and write the combined text to the file newfile.txt. Again, if newfile.txt does not already exist, it will be created; if it already exists, it will be overwritten.
Append a text file's contents to another text file
Instead of overwriting another file, you can also append a source text file to another using the redirection operator ">>".
For instance:
...will read the contents of mytext.txt, and write them at the end of another-text-file.txt. If another-text-file.txt does not already exist, it will be created and the contents of mytext.txt will be written to the new file.
The cat command also works for multiple text files as well:
...will write the combined contents of mytext.txt and mytext2.txt to the end of another-text-file.txt.
Incorporating standard input into cat output
cat reads from standard input if you specify a hyphen ("-") as a file name. For example, if you have a file, list.txt, which contains the following text:
...you could use the echo command to output text, pipe that output to cat, and instruct cat to catenate it with the file's contents, like this:
...which would output the following text:
In short, cat is a simple but very useful tool for working with the data in text files, system logs, configuration files, and any other human-readable data stored in a file.
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Syntax
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Options
這些選項在大多數Linux 發行版中的標準GNU cat上可用。如果您使用的是其他類似Unix的操作系統（例如BSD），則其中某些選項可能不可用；請參閱第133頁上的“選擇”。請查看您的特定文檔以獲取詳細信息。
-A, --show-all
等效于-vET。
-b, --number-nonblank
編號非空輸出線。此選項覆蓋-n。
-e
等效于-vE。
-E, --show-ends
在每行末尾顯示“ $ ”。
-n, --number
編號所有輸出線。
-s, --squeeze-blank
抑制重復的空輸出線。
-t
等效于-vT。
-T, --show-tabs
顯示TAB字符^I.
-v, --show-nonprinting
除LFD和TAB外，請使用^和M-表示法。
--help
顯示幫助消息，然后退出。
--version
輸出版本信息，然后退出。
These options are available on GNU cat, which is standard on most Linux distributions. If you are using a different Unix-like operating system (BSD, for example), some of these options may not be available; check your specific documentation for details.
-A, --show-all
Equivalent to -vET.
-b, --number-nonblank
Number non-empty output lines. This option overrides -n.
-e
Equivalent to -vE.
-E, --show-ends
Display "$" at end of each line.
-n, --number
Number all output lines.
-s, --squeeze-blank
Suppress repeated empty output lines.
-t
Equivalent to -vT.
-T, --show-tabs
Display TAB characters as ^I.
-v, --show-nonprinting
Use ^ and M- notation, except for LFD and TAB.
--help
Display a help message, and exit.
--version
Output version information, and exit.
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Examples
讀取file.txt的內容并將其顯示在屏幕上。
讀取file1.txt和file2.txt的內容，并在終端屏幕上按順序顯示它們。
讀取file.txt的內容并將它們寫入newfile.txt，覆蓋先前包含的所有newfile.txt。如果newfile.txt不存在，將創建它。
閱讀file.txt的內容，并將其附加到another-file.txt的末尾。如果another-file.txt不存在，將創建它。
顯示file.txt的內容，省略任何重復的空白行。
Read the contents of file.txt and display them on the screen.
Reads the contents of file1.txt and file2.txt, and displays them in order on the terminal screen.
Read the contents of file.txt and write them to newfile.txt, overwriting anything newfile.txt previously contained. If newfile.txt does not exist, it will be created.
Read the contents of file.txt and append them to the end of another-file.txt. If another-file.txt does not exist, it will be created.
Display the contents of file.txt, omitting any repeated blank lines.
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其他命令行
cut | cu | csplit | crontab | cpio | continue | compress | col | cmp | cksum | chsh | chroot | chkey | cd | chmod | cp | comm | chown | cal | calendar | clear | chfn | cancel | cc | cfdisk | checkeq | checknr | chgrp |