Cat CDCHMOD Chowncp CUT
Name: CAT Use Permissions: All users use mode: cat [-abeensttuv] [--help] [--Version] filename Description: Connect the file to the basic output (screen or plus> filename to another) Parameters: -N or --Number is similar to the number of rows numbers -b or -number-nonblank and -n of all outputs, but it is encountered for blank lines - Square On two consecutive rows of blank lines, it is changed to the blank line of the line -V or -Show-nonprinting
Example: cat -n textfile1> textfile2 Plus TextFile1 files After adding the line number, enter the textfile2. Cat -b textfile1 textfile2 >> TextFile3 adds the file content of TextFile1 and TextFile2 to add the line number (blank line does not add) TEXTFILE3
Name: CD Usage Permissions: All users
How to use: CD [DIRNAME]
Description: Transform work catalog to Dirname. The DiRName representation can be an absolute path or relative path. If the directory name is omitted, transform to the user's Home Directory (that is, the directory where Login is located).
In addition, "~" is also expressed as HOME DIRECTORY, "." Means the current directory, ".." indicates the current directory of the current directory location.
Example: Jump to / usr / bin /: cd / usr / bin
Jump to your own home directory: CD ~
Jump to the upper two layers of the current directory: cd ../ ..
Directive Name: CHMOD Usage Permissions: All users
How to use: chmod [-cfvr] [--help] [--version] mode file ...
Description: Linux / UNIX file access rights are divided into three levels: file owners, groups, others. Using CHMOD how to control the file is accessed by others.
Tie count:
Mode: Permissions set strings, formats are as follows: [Ugoa ...] [ - =] [RWXX] ...] [, ...], where u indicates the owner of the file, G represents the file The owner belongs to the same group (Group), o other people, a means that these are all. Represents increased permissions, indicates cancellation, = indicates unique setting permissions. R indicates that readable, W represents written, x represents executable, X represents only when the file is a subdirectory or the file has been set to be executed. -c: If this file authority does have changed, it is displayed in the change action -f: If this file authority cannot be changed, do not display the error message-V: Display permission change - R: All files in current directory Permissions change with the subdirectory (ie, changed one by one by hand) - Help: Display Auxiliary Description --Version: Display version
Example: Set the file file1.txt to all people can read: chmod ugo r file1.txt
Setting the file file1.txt to be read: chmod a r file1.txt
Set the file file1.txt and file2.txt to this file owner, with its own same group of groups, but other people cannot write: Chmod Ug W, O-W File1.txt file2.txt
Set an ex1.py to only the file owner can be executed: chmod u x ex1.py
Set all the files and subdirectories in the current directory to anyone can read: ChMOD -R A R * Also CHMOD can also use the number to indicate that the authority of the CHMOD 777 File is: Chmod ABC file
Where A, B, C are each number, which represents USER, Group, and Other permissions.
R = 4, w = 2, x = 1 To RWX attribute 4 2 1 = 7; to RW-attribute 4 2 = 6; if the R-X property is 4 1 = 7.
Example: chmod a = rwx file
CHMOD 777 File
Effects the same chmod ug = rwx, o = x file
CHMOD 771 FILE
Effect
If you use CHMOD 4755 FileName, this program has root permissions
Directive Name: Chown Use Permissions: root
How to use: chmod [-cfhvr] [--help] [--version] user [: group] file ...
Description: Linux / UNIX is multi-person multi-work industry, all of which have owners. Use Chown to change the owners of the file. In general, this instruction only is used by the system administrator (root), and the general user has no permissions to change someone else's file owner, and there is no permission to change the owner of its own files to others. Only the system administrator (root) has such permissions.
Tie count:
User: New Archive owner's user IDGroup: New Archive owner's User Group (Group) -c: If the file owner does have changed, the change action is displayed - F: If the owner cannot Do not display the error message - H: only for links (LINK), not the LINK, true pointing file -V: Display owner change - R: All files and subdirectories in current directory Perform the same owner change (ie, changed one by one by way) - Help: Display Auxiliary Description --Version: Display version
Example: Set the owner of the file file1.txt to the User Group User Jessie: Chown Jessie: Users File1.txt
Use all files in the current directory with the owner of the subdirectory to users of users Lamport: chmod -r Lamport: Users *
Name: CP Use Permissions: All users
Use mode:
CP [options] Source destCP [options] Source ... Directory
Description: Copy a file to another, or copy several files to another directory.
Put on
-a will copy the file status, permissions and other materials as much as possible. -r If the Source contains a directory name, the files in the directory are also copied to the destination. -f If the destination already has the same file, it is deleted before the replication is removed. Example: Copy the file aaa (already existing) and name BBB: CP AAA BBB
Copy all C language to the finished subdirectory: cp * .c finished
Name: CUT
Use permission: All users
Usage: cut-cnum1-num2 filename
Description: Shows the text that counts Num1 to Num2 from the beginning.
example:
Shell >> Cat Examplest2this is test1shell >> Cut -c0-6 example ## print counts the first 6 words Test2this i
Name: Find usage: Find instructions:
List of files that comply with Expression in the archive system. You can refer to a combination of different information such as the name, category, time, size, permissions, etc., only fully matched. Find determines the Path and Expression on the following rules, first on the command - (), the previous part is PATH, after which is Expression. If PATH is a empty string, use the current path, if expression is the empty string, use -print as the preset expression
There are more than two or thirty options that can be used in Expression, which only introduces the most commonly used part.
-mount, -XDEV: Only check and specify files under the same archive system, avoid listing files in other file systems - Amin N: Reads in the past N - Annewer File: More than file file Night-read file -Atime N: Files read in the past N: CMIN N: Changed in the past N: -cnewer file: file updated than file file - CTIME N: in the past N Sky-modified file -empty: empty file -gid n or -group name: GID is n or group name is Name-ipath p, -path P: path name complies with P's file, IPath will ignore the case - Name name, -iname name: The file name is compliant with the file. INAME ignores uppercase-size N: The file size is n unit, b represents the block of 512-bit yuan group, c represents the number of words, and K means kilo bytes, W is two bit groups. -type C: The file type is C file. D: Directory C: Documentary Device Archives B: Block Device Archive P: Total Famous F: General Archive L: Symbol Connection S: SOCKET-PID N: Process ID is N
You can use () to separate the arithmetic, and use the following operations. Exp1 -and Exp2! EXPR-NOT Exprexp1 -or Exp2exp1, Exp2 Example: List of all extended files in the current directory and its subdirectory is C. # Find. -name "* .c"
List all the general files in its underlying directory therefrom # find. -Ftype f
List of all files updated in the current directory and its subdirectory # Find. -Ctime -20
Name: Less
Use permission: All users
Use mode:
Less [option] FileName
Description: The role of Less is very similar to more, can be used to browse the text file, the difference is that the LESS allows the user to scroll back to browse the already seen part, and because the Less does not read at the beginning The entire file, so when you encounter a large file, it will be fast than the general instrument editor (such as VI).
example:
Directive Name: LN Use Permissions: All users
How to use: ln [options] Source Dist, where Option is:
[-bdfinsvf] [-S backup-suffix] [-v {numbered, existing, simple}] [- help] [--Version] [-] Instructions: Linux / UNIX file system, so-called linking ( LINK, we can treat it as an alias of the file, and the link can be divided into two types: hard links and soft links, hard links means that a file can have multiple names, and The soft connection method is to generate a special file, and the content of the file is to point to another file. Hard links are in the same archive system, while soft links can span different archive systems. The LN Source Dist is a link (dist) to SOURCE, as for the use of the hard link or soft link, is determined by the parameter. Whether it is a hard link or soft link, it will not copy a copy of the original file, and will only take a very small amount of disk space.
-f: The file will first delete the file with the DIST: Allow the system administrator hard link to your directory -i: When deleting the file with the DIST, I'm inquiry -N: In progress When the soft link, the Dist is treated as a general file-S: Symbolic link -V: The file name is displayed before the connection - B: Backup of files that will overwrite or deleted during the link - S Suffix: Plus the backup files with the word tail - V Method: Specify the way backup - Help: Display auxiliary instructions --Version: Display version: ZZLN-S Yy ZZ
Generate a Hard Link: ZZLN YY XX with the file yy
Name: Locate Usage Permissions: All users use mode: locate [-q] [-d] [--Database =] locate [-r] [--Regexp =] locate [-qv] [-o] [- Output =] locate [-e] [-f] <[- l] [-c] <[- u] [-u]> locate [-VH] [--Version] [--help] Description: Locate let Users can quickly search for the specified file in the archive system. Its method is to build a database including all file names and paths in the system, and then only query this database when looking for, without having to go deep into the archive system.
In a general distribution, the establishment of the database is placed automatically in the contab. General users use as long as used
# locate your_file_name
The model is OK. Parameters: -U-U
Establish a database, -U will start by the root directory, and -U can specify the starting position.
-e
Will exclude the range of findings.
-l if it is 1. Start safe mode. In safe mode, the user will not see the file that is not available. This will slow down because Locate must obtain the permission information of the file in the actual archive system.
-f Examples of specific archives systems, for example, we have not to put the files in the proc archive system in the database.
-q quiet mode does not display any error messages.
-N is displayed to display an output.
-r Use a regular arithmetic condition for the condition.
-o Specifies the name of the stock.
-d
Specify the path to the database
-h display auxiliary message
-v Show more messages
-V display version of the version of the message:
LOCATE chDRV: Looking for all files called ChDRV locate -n 100 a.out: Look for all files called A.out, but only 100 locate -u: Establish a database
Name: LS Use Permissions: All users
How to use: ls [-ALRTAFR] [name ...]
Description: Displays the contents of the specified working directory (list the files and subdirectories included in the current working directory). -A Displays all files and directories (LS instead of starting the archive name or directory name "." is considered hidden file, not listed) -L In addition to the file name, file type, permissions, owner, The size of the file is detailed -R -R to display the file in the opposite order (original alphabetical order) -t list -A -A-A, but not listed "." (Current) Directory) and ".." (parent directory) -f plus a symbol after listed; for example, the executable is added "*", the directory is added "/" - r If there is a file in the directory, the following The archives are also listed sequentially
Example: List all the names in the current working directory, the beginning of the beginning, the getting upset behind: ls -ltr s *
List all directories and file details below / bin directory: ls -lr / bin
List all files and directories in the current work directory; directory is then added "/", and the file can be executed after the name is added "*": ls -af
Name: More Use Permissions: All users use methods: more [-dlfpcsu] [-num] [ / pattern] [ LINENUM] [filenames ..] Description: Similar to CAT, it will be convenient in one page The user is reading page by page, and the most basic instruction is to press the blank key (Space) to display the next page, press the B button to come back (back) one page, and there is also the function of searching strings (with VI Similarly, in use, press H. Parameters: -Num The number of rows -D prompt users, display [Press Space to Continue, Q to Quit.] Below the screen, if the user presses the wrong button, [Press H for instructions.] Instead of Beep-L cancels the number of function -f calculating rows when the special font ^ L (paper feed character) is met, the number of rows after the actual line, not the number of rows after the automatic wrap (some single line words It will be extended to two rows or more.) -P does not display each page in a row, but first cleared the screen, then display the content-C and -p, the difference is to display the content and then clear other Old Data-S When there is a blank line with two consecutive lines, the blank line-U does not display the lower quotation marks (depending on the TERMINAL specified by the environment variable TERM) / in each file display Search for the string (Pattern), then start displaying from the string NUM Start displaying filenames from the NUM row to display files to display the contents of the content, can be used as a number of quotable examples: more -s testfile Displays the file content of Testfile If there are two consecutive lines of blank lines display in a row of blank lines. More 20 Testfile starts the contents of Testfile from the 20th line.
Name: MV Use Permissions: All users
Use mode:
MV [Options] Source Destmv [Options] Source ... Directory Description: Move a file to another, or move several files to another directory. Parameters: -i If the destination already has the same name file, first ask if the old file is overwritten.
example:
Rename the file AAA to BBB: MV AAA BBB
Move all C language programs to the finished subdirectory: mv -i * .c Name: RM Use Permissions: All users
How to use: rm [options] name ...
Description: Delete files and directories.
Put on
-i before the deletion, please ask for confirmation one by one. -f even if the original file property is set to read, it is also directly deleted without one by one. -r Detects the directory and below. Example: Delete all C language program files; ask for a one before deleting confirmation: rm -i * .c
Remove all files in the Finished subdirectory and subdirectory: RM -R Finished
Name: RMDIR Use Permissions: All users with appropriate permissions in current directory
How to use: rmdir [-p] DIRNAME
Description: Delete empty directories.
Parameters: -P is that when the subdirector is deleted, it will also be deleted by the way.
example:
Remove the subdirectory named AAA in the working directory: RMDIR AAA
In the BBB directory in the working directory, delete the subdirectory called TEST. If the Test is deleted, the BBB directory is empty, then BBB is also deleted. RMDIR -P BBB / TEST
Name: SPLIT Use Permissions: All users
How to use: split [option] [INPUT [Prefix]
Description:
Split a file into several files. From the INPUT division output into a fixed-size file, its file name is prefixaa, prefixab ...; prefix preset value `x. If there is no input file or `-, you will be read from the standard input.
匡 兜
-b, --Bytes = Size
The size value is the size of each output file, and the unit is BYTE. -C, --Line-bytes = size
In each output, the maximum number of BYTEs in a single line. -L, --Lines = Number
The Number value is the size of the column size of each output. -Number
The same as -l Number. --Verbose
Print the detection information to standard error output before each output file is opened. --help
Display auxiliary information and then leave. --Version
Listed by this information and then leave. Size can join the unit: b represents 512, K represents 1k, M represents 1 meg.
example:
Postgressql Large Data Library Backup and Recycling:
Because Postgres allows the form to have a largest capacity of your system file, it is possible to have problems with table dump to a single file, and Split is used to divide.
% PG_Dump DBNAME | SPLIT -B 1M - FileName.dump.
Reload
% createDb dbname% cat filename.dump. * | PGSQL DBNAME
Name: Touch Use Permissions: All users
How to use: Touch [-ACFM] [- r Reference-file] [--file = reference-file] [- t mmddhhmm [cc] yy] [. S] [- d time] [--date = time] [ --Time = {Atime, Access, Use, Mtime, Modify}] [- no-create] [--help] [--version] file1 [file2 ...]
Description: Touch instruction changes the time record of the file. LS -L can display the time record of the file.
Parameters: a Changing the read time record of the file. m change the modification time record of the file. C If the purpose file does not exist, it will not establish a new file. Like -No-Create. F is not used, is to retain to compatibility with other UNIX systems. r Use the reference file time record, like the effect of thefile. D Setting time and date, you can use a variety of different formats. T Time Record of the file is set, the format is the same as the DATE instruction. --NO-CREATE does not establish a new file. --Help lists the instruction format. --Version lists this message. example:
The simplest way of use, change the file when you record the time. If the file does not exist, a new file will be established.
Touch filetouch file1 file2
Change the time record of File to 18:3:39 on May 6, 2,000 years. Time format can refer to the Date directive, at least you need to enter MMDDHHMM, which is the time of months and minutes.
Touch-C -T 05061803 FileTouch -c -t 050618032000 file
Change the File time record into ReferenceFile.
Touch -R ReferenceFile File
The time record of File is changed to 18:3:36 on May 6, two thousand years old. Time can be used in AM, PM or 24-hour format, and other formats can be used in other formats such as 6 May 2000.
Touch -d "6:03 PM" FileTouch -d "05/06/2000" FileTouch -d "6:03 PM 05/06/2000" File Name: AT Usage Permissions: All users
How to use: At -V [-q queue] [-f file] [-mldbv] Time
Description: AT allows the user to specify a certain number or instruction in Time, TIME's format is HH: mm, the HH of HH is hour, MM is minutes, or you can specify AM, PM, Midnight, Noon, Teatime (is 4 pm).
If you want to specify the time in more than a day, you can use mmddyy or mm / dd / yy format, where mm is minute, DD is the day, yy refers to the year. In addition, the user can even use a NOW time interval to elastic designation time, where the interval can be Minutes, Hours, Days, Weeks
In addition, the user can also specify Today or Tomorrow to represent today or tomorrow. When the time is specified and press Enter, the AT will enter the conversation mode and ask for input instructions or programs. When you press CTRL D, press Ctrl D to complete all the actions, as for the result of the execution, will be sent back to your account .
Tie count:
-V: Print Publish No. -Q: Use the specified 伫 伫 (Queue) to store, the data of the AT is stored in the so-called queue, and the user can use multiple queue at the same time, and the number of Queue is A, B, C ... Z and A, B, ... Z Total 52 - M: Even if the program / instruction is executed, there is no output result, but also send a letter to the user -f file: read the pre-write command files. Users do not have to use the conversation mode to enter, first write all the specified first to the file once again read -L: List all the specified (the user can also use ATQ directly without AT -L) -D : Delete the specified (the user can use ATRM directly without AT -D) -V: list all completed but not yet deleted specified
Example: 5 pm after three days of exercise / bin / ls: at 5pm 3 days / bin / ls three weeks later 5pm to execute / bin / ls: AT 5PM 2 Weeks / Bin / LS
Tomorrow's 17:20 execution / bin / date: at 17:20 Tomorrow / BIN / DATE
The last day of 1999 printing the end of world! At 23:59 12/31/1999 echo the end of world!
Name: CAL
Use permission: All users
How to use: Cal [-mjy] [MONTH [YEAR]
Description:
Display calendar. If there is only one parameter, it represents the year (1-9999), showing the annual calendar. The year must be written: `` Cal 89 will not show the annual calendar of 1989. Use two parameters, indicating the month and year. If there is no parameter, this month's calendar is displayed. September 3rd on September 1752, the Western calendar, because most countries used a new calendar, 10 days of removal, so the monthly calendar of the month is somewhat different. It was before this.
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-M: Displayed on weekdays for weekly first day. -J: Displayed by Kaisa, that is, the number of days from January 1 is displayed. -y: Show this year calendar.
example:
CAL: Shows the monthly calendar of this month.
[root @ mylinux / root] # DateTue aug 15 08:00:18 cst200 [root @ mylinux / root] # calaugust 2000su mo Tu we TH fr sa1 2 3 4 56 7 8 9 10 11 1213 14 15 16 17 18 1920 21 22 23 24 25 2627 28 29 30 31
[root @ MYLINUX / root] #
CAL 2001: Shows the annual calendar of AD.
[root @ mylinux / root] # CAL 20012001
January February Marchsu Mo Tu We TH fr Su Tu We TH fr Sa1 2 3 4 5 6 1 2 3 1 2 37 8 9 10 11 12 13 4 5 6 7 8 9 10 4 5 6 7 8 9 1014 15 16 17 14 15 16 17 11 12 13 14 15 16 1721 22 23 24 25 25 26 27 18 19 20 21 22 23 23 2428 29 30 31 25 26 27 28 25 26 27 28 29 30 31
April May Junesu Mo Tu We TH fr SU Mo Tu We TH fr Sa1 2 3 4 5 6 7 1 2 3 4 5 1 28 9 10 11 12 13 14 6 7 8 9 10 11 12 3 4 5 6 7 8 915 16 17 18 19 20 21 13 14 15 16 17 18 1922 23 24 25 26 27 28 20 21 22 23 24 25 26 17 18 19 20 21 22 2329 30 27 28 29 30 31 24 25 26 27 28 29 30
July August Septembersu Mo Tu We TH fr SU Mo Tu We TH fr SU Mo Tu We TH fr SA1 2 3 4 5 6 7 1 2 3 4 18 9 10 11 12 13 14 5 6 7 8 9 10 11 2 3 4 5 6 7 815 16 17 18 19 20 21 12 13 14 15 16 17 18 9 10 11 12 13 14 1522 23 24 25 26 27 28 19 20 21 22 23 24 24 2229 30 31 26 27 28 29 29 30 31 23 24 25 26 27 28 2930OCTOBER NOVEMBER Decembersu Mo Tu We TH fr SU Mo Tu We TH fr sa su mo tu we th Fr Sa1 2 3 4 5 6 1 2 3 17 8 9 10 11 12 13 4 5 6 7 8 9 10 2 3 4 5 6 7 814 15 16 17 18 19 20 11 12 13 14 15 16 17 9 10 11 12 13 14 1521 22 23 24 25 26 27 18 19 20 21 222 23 24 16 17 18 19 20 21 2228 29 30 31 25 26 27 28 29 30 23 24 25 26 27 28 2930 31 [root @ mylinux / root] #
CAL 5 2001: Shows AD in May 2001.
[root @ mylinux / root] # CAL 5 2001May 2001su Mo Tu We TH fr Sa1 2 3 4 56 7 8 9 10 11 1213 14 15 16 17 18 1920 21 22 23 24 25 2627 28 29 30 31
[root @ MYLINUX / root] #
Cal -m: The first day of week is the week, showing this month.
[root @ MYLINUX / ROOT] # Cal -maugust 2000Mo Tu We TH fr sa su1 2 3 4 5 67 8 9 10 11 12 1314 15 16 17 18 19 2021 22 23 24 25 26 2728 29 30 31
[root @ MYLINUX / root] #
Cal -jy: Displays the number of days from January 1st.
[root @ mylinux / root] # Cal -jy2000
January FebruarySun Mon Tue Wed Thu Fri Sat Sun Mon Wed Thu Fri Sat1 32 33 34 35 37 39 39 40 41 42 439 10 11 12 13 14 15 44 45 46 47 48 49 5016 17 18 19 20 21 22 51 52 53 54 55 56 5723 24 25 26 27 28 29 58 59 6030 31march Aprilsun Mon Tue Wed Thu Fri Sat Sun Mon Tue Wed Thu Fri Sat61 62 63 64 9265 66 67 68 69 70 71 93 94 95 96 97 98 9972 73 74 75 77 103 104 105 10679 80 81 82 83 84 85 107 108 109 110 111 112 11386 87 88 89 90 91 114 115 116 117 118 119 120121May Junesun Mon Tue Wed Thu Fri Sat Sun Mon Tue Wed Thu Fri Sat122 123 124 125 126 129 130 131 132 133 134 156 157 158 137 168 139 140 141 163 164 165 166 167 168 169142 143 144 145 146 147 148 170 171 172 173 174 175 176149 150 151 152 177 178 179 180 181 182july Augustsun Mon Tue Wed Thu fri sat sun mon tue wed tu fri sat183 214 215 216 217 188 189 190 219 220 221 222 223 224 225191 192 193 194 195 196 197 226 227 228 229 229 230 231 2 32198 199 200 201 202 203 204 233 234 235 236 237 238 239205 206 207 208 209 210 211 240 241 242 243 244212 213September OctoberSun Mon Tue Wed Thu Fri Sat Sun Mon Tue Wed Thu Fri Sat245 246 275 276 277 278 279 280 281247 248 249 250 251 252 253 282 287 288254 255 256 257 258 259 260 289 294 291 292 292 263 264 265 266 267 296 297 298 299 300 301 302268 274 303 304 305 305
November DecemberSun Mon Tue Wed Thu Fri Sat Sun Mon Tue Wed Thu Fri Sat306 307 308 309 336 337310 311 312 313 314 315 316 338 339 340 341 342 343 344317 318 319 320 321 322 323 345 346 347 348 349 350 351324 325 326 327 328 329 330 352 353 354 355 356 357 358333 332 333 334 335 359 360 361 362 363 364 365366
[root @ MYLINUX / ROOT] # Name: crontab Usage Permissions: All users
Use mode:
Crontab [-U user] filecrontab [-u user] {-l | -r | -e} Description: crontab is used to make users in fixed time or fixed interval executable, in other words, similar to use Time history. -u user refers to the schedule that sets the specified user. This premise is that you have to have its permissions (such as root) to specify the schedule of others. If you don't use -u user, it means to set your own schedule.
Number of meals:
-e: Perform a text editor to set a time program, the contents of the text editor is VI. If you want to use the other text editor, please set the Visual environment variable to specify the use of that text editor (for example STENV Visual Joe) -r: Delete the current Turkey -L: List the current schedule
The format of the schedule is as follows: F1 F2 F3 F4 F5 Program
Where F1 is a minute, F2 represents hours, and F3 represents the first few days in one month, and F4 represents the month, F5 represents the first few days in the week. Program represents the program to be executed. When F1 is *, the Program is executed every minute, and the F2 is * indicates that the program is executed per hour, and the remaining classes have been applied to the first time to be AB, which is executed from the first minutes to the third time, F2 is When AB is executed from paragraphs A to B, the remaining classes are pushed to * / n when the f1 is * / N, indicating that each time interval is executed once, and F2 is * / n to execute each time time interval, the remaining classes When F1 is A, B, C, ... is shown in paragraph A, B, C, ... minutes to perform, F2 is A, B, C, ... indicated first, b, c ... Hourly to be executed, the rest
Users can also store all settings first in the file file, and set the time schedule in the way in the CRONTAB FILE. Example:
Perform once a day per hour per hour / bin / ls: 0 7 * * * / bin / ls
In December, 6:00 pm every day, per 20 minutes per 20 minutes / usr / bin / backup: 0 6-12 / 3 * 12 * / usr / bin / backup
