1. #注释作用, #! Except in addition, in the parameter replacement echo ${path#*:} here does not represent the comment, the numeral conversion, does not represent the comment echo $ ((2#101011)) 2. Command line delimiter, you can write multiple commands on a single line. echo Hello; Echo There3. ;; To terminate the case option, copy the code code as follows:
Case "$variable" inabc) echo "\ $variable = abc";; XYZ) echo "\ $variable = xyz";; Esac4. . hide file prefixes. The command is equivalent to source. Represents the current directory: Represents a single character match in the previous level of a directory regular expression
5. "", "double quotes, single quotes, where you can reference variables in double quotes, but not in single quotes, they are organized with special characters 6. \
Escape character 7. /filename delimiter, Division operation 8. ' (the button below ESC)
After the reference, the command replaces 9. :
Null command, equivalent to "NOP" can also be considered as the shell built-in command true function of the same 10. Take the inverse operator! = is not equal to 11. *
Universal match, mathematical multiplication in regular expressions * * Power Operation 12. ? In the test action regular expression,? Matches any single character 13. $ variable symbol regular expression line terminator ${} parameter replace $*,[email protected] Position parameter $? Exit status $$ process ID14. () command group, (A=hello; Echo $a), the list of commands in () runs as a child shell. The variables in () are not available for the remainder of the script because they are in the child shell. Array initialization: array= (element1, Element2, Element3) 15. {XXX,YYY,ZZZ}
Curly braces extend cat {file1,file2,file3} > Combined_file, merging File1,file2,file3 together and redirecting to Commbined_file. Cannot have spaces in curly braces
16. {} code block. In fact, this structure creates an anonymous function. But unlike a function, the variable declared in it is still visible to the code of the rest of the script. Copy code code as follows: # Content in code block, external access, I/O redirect 1: #!/bin/bash 2:3: File=/etc/fstab 4: 5: # Variables in this code block, external can also access 6: {7:read line1 8:read line2 9:} < $File 10:11:echo "first line in $File I S "12:echo" $line 1 "13:echo 14:echo" Second line in $File is "15:echo" $line 2 "16:17:exit 0# saves the results of a block of code to a file
17. {}\;
Path names, which are generally used in the Find command, are noted; The –exec18 used to end the find command sequence. []test array elements, such as the ARRAY[1]=ABC character range, use 19 in regular expressions. [[]]
The test expression itself is placed in [] 20. (()) Mathematical calculation extension 21. >& >>& >> < redirect scriptname > FileName redirect script output to file, overwrite original content command &> filename redirect Stdou T and stderr to file command >&2 redirect stdout and stderrscriptname >> filename redirection script output to file, add to file end, if no file, create this file. 22 . << <<<
Redirect, << for "here Document", <<< for "here string"
\<, \>
The word boundary in the regular expression is grep ' \<the\> ' Testfile24. Pipeline, analyzing the output of the front command, and outputting the output as input to the command behind
>| forced redirection 26. || Logic or 27. & Background Run command, a command followed by a &, which will indicate that the copy code code is run in the background as follows:
1: #!/bin/bash 2:3: For I in 1 2 3 4 5 6 7 8 9 4:do 5:echo-n "$i" 6:done&
Note that the last done&28 for the For loop. && Logic and
Special characters for Shell scripts
