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| info:basic_commands [2009/09/17 22:17] – created moritz | info:basic_commands [2011/07/22 13:10] – [HTTP/FTP] spelling moritz |
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| ===== Working with Files ===== | ===== Working with Files ===== |
| * <code>ls</code> lists files in current directory. Use <code>ls -al</code> to list all files (including hidden = starting with .) in a long listing. | * ''ls'' lists files in current directory. Use ''ls -al'' to list all files (including hidden = starting with .) in a long listing. |
| * <code>mkdir</code> creates a directory. Specify the directory name after the command. | * ''mkdir'' creates a directory. Specify the directory name after the command. |
| * <code>rm</code> removes files and directories. If directories need to be removed, the <code>-r</code> option must be specified. To force operation, add <code>-f</code>. The last parameters are the files and directories that are to be deleted. Make sure that there are no wrong directories listed! A call to <code>rm -rf /</code> as root is not a good thing. | * ''rm'' removes files and directories. If directories need to be removed, the ''-r'' option must be specified. To force operation, add ''-f''. The last parameters are the files and directories that are to be deleted. Make sure that there are no wrong directories listed! A call to ''rm -rf /'' as root is not a good thing. |
| * <code>file</code> reveals what content type a file is. Use it to test if a file is text, image, binary or whatever. | * ''mv'' moves a file, where path is relative to current directory: mv [path]filename [path]filname |
| * <code>sudo</code> starts a process with super user (=root) capabilities. To start a root shell, use <code>sudo su</code>. If <code>sudo</code> is not installed, use <code>su</code> instead. It requires not the current user's password but the root password. | * ''file'' reveals what content type a file is. Use it to test if a file is text, image, binary or whatever. |
| * <code>less</code> helps to look at what a file stores. | * ''find'' and ''rm'' can be used in combination to delete files found by ''find''. e.g. this will recursively remove all files with extension ''.txt'' in the current directory: ''find . -name \*.txt -print0 | xargs -0 rm''\\ As an alternative, it is possible to use some shell features: ''rm $(find -name \*.txt)'' |
| * <code>cat</code> reads a file and prints it to <code>stdout</code> (the console if invoked as-is.) | * ''sudo'' starts a process with super user (=root) capabilities. To start a root shell, use ''sudo su''. If ''sudo'' is not installed, use ''su'' instead. It requires not the current user's password but the root password. |
| * <code>locate</code> locates all files that contain a given string. | * ''less'' helps to look at what a file stores. |
| * <code>grep</code> searches input for matching lines. To search all files in the current directory (and sub directories), use <code>grep -r . -e "text"</code>. | * ''cat'' reads a file and prints it to ''stdout'' (the console if invoked as-is.) To read from STDIN, pass ''-'' as the file to read. This can be used to create a file by entering its content in the console. Use ''cat - > new_file'' and paste the content to quickly create a new file with content. To end the file, press Ctrl+D, which produces the EOF-character. |
| * <code>man</code> shows the manual for some command. Sometimes <code>info</code> shows a more detailed documentation. | * ''locate'' locates all files that contain a given string. |
| * <code>dmesg</code> prints kernel messages. | * ''grep'' searches input for matching lines. To search all files in the current directory (and sub directories), use ''grep -r . -e "text"''. |
| | * ''man'' shows the manual for some command. Sometimes ''info'' shows a more detailed documentation. |
| | * ''dmesg'' prints kernel messages. |
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| | ===== Networking Tools ===== |
| | ==== HTTP/FTP ==== |
| | * Use ''wget'' to download files from HTTP and FTP. The tool allows recursive downloading, i.e. also fetch outgoing links from some HTML page. To restrict the files downloaded to a certain type (by file suffix), use the ''-A'' option: <code>wget -r http://some.host/path/to/file.html -A pdf</code> downloads all PDFs referenced by the HTML file. |
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| ===== Piping ===== | ===== Piping ===== |
| The output of one command can be piped into the input of another command. This is done by the pipe operator <code>|</code>. To search kernel messages for some string, use <code>dmesg | grep string</code>. | The output of one command can be piped into the input of another command. This is done by the pipe operator ''|''. To search kernel messages for some string, use ''dmesg | grep string''. |
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| | Additionally, the STDOUT (1) and STDERR (2) streams can also be redirected. To redirect the STDERR output to STDOUT, use: ''command 2>&1 ...''. This can be used in combination with piping. |
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