[Shell, 1] chmod and find commands:

Command: 1. Modify the chmod permission:

The general format of the chmod command is: chmod [who] operator [permission] filenamew h o. The meaning of o is: u file master permission. G. O other user permissions. A. All users (file owner, users in the same group, and other users ). Operator meaning: + add permissions. -Cancel the permission. = Set permissions. Permission: r read permission. W write permission. X execution permission. S file owner and group s e t-I D. T viscosity position *. L lock the file to make it inaccessible to other users. U, g, o operations on file owners, users in the same group, and other users. Example: chmod a-x myfile rw-Revoke the execution permission of all users chmod og-w myfile rw-r -- r-Revoke the write permission of the same group of users and other users chmod g + w myfile rw-r--grant the write permission to the same group of users chmod u + x myfile rwx rw-r--grant the file owner the execution permission chmod go + x myfile rwx rwx r-x grant the same group of users and other users the execution permission chmod 666 rw-grant all users the read and write permissions chmod 644 rw-r -- r--grant all file owner's read and write permissions, all other user read permissions chmod 744 rwx r -- r-grant the file owner read, write, and execute permissions, all other users read chmod 664 rw-r--grant the file owner and the same group users read and write permissions, read Permission of other users chmod 700 rwx --- grant the file owner the read, write, and execute permissions chmod 444 r -- r--grant all users the read permission

2. find command: ①. Search by file name and use the name option.

Regardless of the current path, if you want to find a file with a file name *. t x t in your root directory $ HOME, use ~ As the pathname parameter, the Tilde ~ Represents your $ h o m e directory. $ Find ~ -Name "*. txt "-print: search for all '* in the current directory and subdirectory '*. t x t' file, which can be used: $ find. -name "*. txt "-print: find the file name starting with an uppercase letter in the current directory and subdirectory. You can use: $ find. -name "[A-Z] *"-print: $ find/etc-name "host *"-print to search for files in the $ h o m e directory, you can use: $ find ~ -Name "*"-print or find.-print: to enable the system to run at high load, search for all files from the root directory. If you want to keep a good impression on the system administrator, you 'd better consider it before doing so! $ Find/-name "*"-print if you want to find the file name in the current directory starting with two lower-case letters, followed by two numbers, and finally *. t x t file, the following command returns the name a x 3 7. t x t file: $ find. -name "audio a-z1_a-z1_1_0--91_0--91_.txt"-print

② Search by File Permission mode: Use the perm option:

To find a file with a permission of in the current directory, that is, the file owner can read, write, and execute the file. Other users can read and execute the file: $ find. -perm 755-print: If you want to find all files that can be read, written, and executed by all users in the current directory (Be careful with this situation ), we can use the-p e r m option of the f I n d command. Add a horizontal bar before the octal digit -. In the following command,-p e r m indicates searching by File Permission, the expression '0 0 7' is exactly the same as that used in the absolute mode of the c h m o d command. $ Find.-perm-007-print

③ Ignore a directory and use the-prune option:

If you want to ignore a directory when searching for a file because you know that there is no file in the directory, you can use the-p r u n e option to specify the directory to be ignored. Be careful when using the-p r u n e option, because if you use the-d e p t h option at the same time, the-p r u n e option is ignored by the f I n d command. If you want to search for files in the/a p s directory, but do not want to search for files in the/a p s/B I n directory, you can use: $ find/apps-name "/apps/bin"-prune-o-print

④ Search by file owner: Use the user and nouser options:

If you want to search for a file by file owner, you can give the corresponding user name. For example, to find a file whose owner is d a v E in the $ h o m e directory, you can use: $ find ~ -User dave-print: In the/e t c directory, find the file whose owner is u c p: $ find/etc-user uucp-print in order to find files that have been deleted by the owner account, you can use the-n o u s e r option. In this way, you can find files with no valid account in the/e t c/p a s w d file of the owner. When you use the-n o u s e r option, you do not need to give a user name. The f I n d command can complete the corresponding work for you. For example, to search for all such files in the/h o m e directory, you can use: $ find/home-nouser-print

⑤ Search by file group and use the group and nogroup options:

Like the u s e r and n o u s e r options, the f I n d command also has the same options for the user group to which the file belongs, to search for files belonging to the c t s user group under the/a p s directory, you can use: $ find/apps-group accts-print to find all files in the user group that do not have a valid value, you can use the n o g r o u p option. The following f I n d command looks for such a file from the root directory of the file system $ fine/-nogroup-print

6. Select the type option based on the file type:

If you want to find all directories in the/etc directory, you can use: $ find/etc-type d-print to find all types of files except directories in the current directory, available: $ find .! -Type d-print: To find all symbolic link files under the/e t c directory, you can use: $ find/etc-type l-print

7. Use the-mtime option to search for files based on the Change Time:

You can use the m t I m e option to search for files based on the change time. If the system suddenly has no available space, it is very likely that the length of a file will grow rapidly during this period, then you can use the m t I m e option to find such a file. Use minus signs-to limit the files whose change time is earlier than n days ago, and use the plus sign + to limit the files whose change time is earlier than n days ago. To search for files whose modification time is less than 5 days in the root directory of the system, you can use: $ find/-mtime-5-print to search for files whose change time was earlier than 3 days in the/v a r/a d m directory, you can use: $ find/var/adm-mtime + 3-print

To execute the shell command:

After matching some files, you may want to perform some operations on them. Then you can use the-e x e c option. Once the fi n d command matches the corresponding file, you can use the command in the-e x e c option to operate on it (in some operating systems, only the-e x e c option is allowed to execute commands such as l s or ls-l. ). The e x e c option is followed by the command to be executed, followed by a pair of characters {}, a space, a \, and a semicolon. To use the ls-l command to list the matched files, you can place the ls-l command in the-e x e c option of the f I n d command. For example:

Find.-type f-exec ls-l {}\; To find and delete files whose modification time is earlier than 5 days in the/l o g s directory, you can use: $ Find logs-type f-mtime + 5-exec rm {}\;Usage of commands such as seek, find, and xargs: It seems that xargs has the same function as exec.

The following example finds the memory information dumping file (core dump) in the entire system, and then saves the result to/tmp/core. in the log file: $ find. -name "core"-print | xargs echo "">/tmp/core. in the example of log, search for all files with read, write, and execution permissions under the/a p s/a u d I t directory, and revoke the write permissions: $ find/apps/audit-perm-7-print | xargs chmod o-w in the following example, we use the g r e p command to search for the word d e v I c e in all common files: $ find/-type f-print | xargs grep "device" in the following example, we use the g r e p command to search all common files in the current directory for the word d B O: $ find. -name \ *-type f-print | Xargs grep "DBO" NOTE: In the preceding example, \ is used to cancel the special meaning of * in shell of the find command.