shell scripting basics

Shell BASICS (5) condition judgment and shell Basics When writing a script, you sometimes need to judge whether the strings are equal and test the number. This lays the foundation for the shell statements, loops, and condition statements learned later. Condition judgment fo

Shell scripting is an essential skill for Linux OPS engineers and a very important skill, so it's only good to learn shell programming well. Basic grammar I will not speak, learn the C language of these languages, a little bit to understand the basis of shell programming, so we directly cut to the point.The 20th day of

environmental changes to the parent shell. 2. Use parentheses () Running a command in () also opens a child shell. So do not randomly write () in Linux to change the priority, unless it is escaped, and the parentheses after the turn to have a space between the contents of the parentheses. [Email protected] tmp]# echo $BASH _subshell 0 [Email protected] tmp]# (echo $BASH _subshell) 1 ? Description opens a

Linux shell programming 1 ---- shell script programming basics 1 What is shell script 1 shell is not only a command interpreter but also a programming language, a program written in shell is similar to a batch processing program i

out the last/and left string: my.file.txt${file#*.} Take out the first one. And the string to the left: file.txt${file##*.} Take off the last one. And the string to the left: txt${file%/*} take out the last/And right string:/dir1/dir2/dir3${file%%/*} take out the first/and the right string: (null value)${file%.*} take off the last one. And the string to the right:/dir1/dir2/dir3/my.file${file%%.*} take off the first one. And the string to the right:/dir1/dir2/dir3/myTest.sh:File=dir1/dir2/dir3/

been set. [-H file] True if file exists and is a symbolic connection. [-K file] True if file exists and the sticky bit has been set. [-P file] If file exists and is a name pipe (f if O) is true. [-R File] True if file exists and is readable. [-S file] True if file exists and the size is not 0. [-T FD] true if the file descriptor FD is open and points to a terminal. [-u file] True if file exists and suid (set user ID) is set. [-W file] True if file exists and is writable. [-X file] True if file

result is"$sum; Filearray=`ls./files/*. txt '; for file in $filearraydoecho $filedone11. Shake the PanFinally, I wish you ...Because other execution statements can be arbitrarily inserted into the shell script, we can sometimes ask the high-level language or other familiar script to perform some operations. This is where the shell is powerful and flexible.For example, we can write a C + + file#include type

Tags: distinguishing string roo Interactive process%s usage definition function efficiencyFirst, Shell script introductionThe shell is a scripting language, and the shell is a collection of system commands1, can use logic judgment, cycle and other grammar;It's a bit like C language, but it's fundamentally different.2,

command willSHELLmeta-characters are expanded. 4. In the double-brace Test command, if a string (with or without a space) is simply the expression as a normal string, not part of a pattern, it must also be enclosed in quotation marks. If a string value (the one on the right) is not enclosed in double quotes, the string is a pattern, and if it contains SHELL metacharacters, bash expands it. If the string is double-quoted, it is a very ordinary string

substitution or deletion stty locale display locale settings # Replace the "ABC" that appears in the file with "XYZ"Cat file| tr "Abc" "Xyz"> New_file# Use the TR command to "unify" the case of lettersCat file| tr [A-z] [a-z] > New_fileCat file| tr [A-z] [a-z] > New_file# Replace the number 0-9 in the file with A-jCat file| tr [0-9] [a-j] > New_file# Delete the "Snail" characters that appear in file files

redirect to generate a patch file:[Email protected]:~/dl$ diff-u version1.txt version2.txt > Version.patch[Email protected]:~/dl$ cat Version.patch---version1.txt 2015-12-28 19:16:28.866869790 +0800+ + + version2.txt 2015-12-28 19:17:12.078872041 +0800@@ -1,5 +1,5 @@This is the original text-line2-line3+lin2Line4Happy hacking!+gnu is not UNIXUse the following command to Patch:[Email protected]:~/dl$ patch-p1 Version1.txt Patching file Version1.txt[Email protected]:~/dl$ cat Version1.txtThis is

value of a running process Renice-n PIDNohup SH executes scripts in the backgroundCtrl Z hangs a foreground processFG Job Number The file foreground runs the BG job number to run the file background/proc DirectoryShell Scripts Scripta shell script is a text file that contains a shell directiveShell and oh ah this supports variables with simple syntax to complete batch workHow

function is like a mini script that can be passed when calling a functionAny parameter, within the function is also used to extract parameters such as $, $, $, etc., the position parameter in the function is equivalent to the functionLocal variables, changing these variables does not affect variables such as $, $, $, and so on outside the function. function, you can use returnCommand returns if the return followed by a number represents the exit Status of the function.For example:650) this.widt

No orders found. 128 Invalid exit parameter 128+x Critical error for Linux signal x 130 Command terminated with CTRL + C 255 Exit status code out of bounds Exit Exit command can specify exit status code, but not more than 255, otherwise it will be moduloCode 1-16[Email protected]:/data# cat Demo4 #!/bin/bashdateecho $?whoexit 5[email protected]:/data#./demo4 Fri Dec 2 05:03:08 CST 20160root pts/

included file test1.sh does not require executable permissionsRun a python script in a shell scriptTry to run the Python script in the shell script, if the Python script contains the shell's illegal statements, the above mentioned two methods are not possible, this may indicate that the above method is only for Shell script calls. It is also convenient to run Py

"######---Number of CPU threads---#######" echoprocessor=' echo $CPU ' if[ $CPU -eq4];then ' echo ' wa= $WA andid= $ID Cpuprocessorisok "|mail-s" $HOST cpu "[emailprotected] ' Else ' echo "wa= $WA andid= $ID cpuprocessorhaveproblem" |mail -s "$HOST cpu" [emailprotected] ' fiecho "######---CPU ID---#########" echo Cpu~id= ' echo $ID ' echo ' ######---CPU wa---######### ' echocpu~wa= ' echo $WA ' echo ' ###### ---CPU load---####### "echocpu-load= ' echo $LOAD ' if[ $LOAD >0.05];then ' echo ' cpu

variable), returns the old value to the variable after the result has been generated, and then executes the variable plus 1 operation. In contrast, in the prefix (prefix), the operand is placed in front of the variable, the variable is added 1, and then return the new value to the variable,--the working method and + + is similar, but its operation is to reduce the variable by 1.7. Exit statusEach command exit returns a small integer value to the program that refers to it, which is the well-know

Tags: shell script1, write script/root/bin/systeminfo.sh, display the current host system information, including hostname, IPV4 address, operating system version, kernel version, CPU model, memory size, hard disk size#!/bin/bashecho "hostname: `hostname`"echo "ipv4 addr: `ifconfig |egrep -o "\2, scripting/root/bin/backup.sh, can be implemented to backup/etc/directory to/ROOT/ETCYYYY-MM-DD#!/bin/bashecho "co