Shell's scripting Exercises

make a demand flow chart requirement Analysis-Program Design-specific implementation of training pointssed,Echo, Test,if, while,Shift1. Demand Analysis: Practice Test-d Scheme design: reflect the idea, first define a variable, with the conditions to determine the specific implementation: input: The following [[email protected] --shiyanSH]#Cat>Mytesta=/root/SH/sedif[ -D $a] ThenEcho "$a is a directory"fioutput: correct satisfaction [[email protected] --shiyanSH]#chmodu+x mytest[[email protected] --shiyanSH]# ./mytest/root/SH/sedis a directory2Requirements Analysis: Although the previous step was implemented, there was only one directory, and was dead and inflexible. And if it is not a directory, there is no corresponding output. Scheme design: Replace directory with file, add non-directory output. Specific implementation: Use SED to modify the source file directly on the command line. You can point to:-E, multiple edits to use. Input: below [[email protected] --shiyanSH]#sed-i-e's/sed/mem/'-E'/echo/a\\else echo "$a is a file"'mytest Output: correct satisfaction [[email protected] --shiyanSH]# ./mytest/root/SH/mem is afile3Requirements Analysis: The directory in the script to death, inconvenient, how to go to the command line to pass the file name parameters, so it is convenient. Project design: Concrete implementation: using SED to directly modify the source file in the command line, comment out the first line of input: [[email protected] --shiyanSH]#sed-i-e'1s/a/#&/'-E's/\ $a/\$1/'Mytest[[email protected] --shiyanSH]#Catmytest#a=/root/SH/Memif[-D $1 ] ThenEcho "is a directory"Else Echo "$ is a file"fioutput: correct satisfaction [[email protected] --shiyanSH]#./mytest for foris afile[[Email protected] --shiyanSH]#./mytestawkawkis a directory4Requirements Analysis: If you can test multiple files or directories on the command line, the scheme design: Add a condition to judge each cycle, and output accordingly. Implementation: Using while loop and shift to realize the uncertainty of the number of positional parameters, the main point: until loop and while loop structure is basically the same, but until is to judge the condition expression is false to continue the loop! Difficulty:-N is the $ that is used to test whether a string is empty*is to display all the parameters passed to the script in a single string, which, unlike positional variables, can have more than 9 parameters that contain all the input command-line parameter values. If you run showrpm openssh.rpm w3m.rpm webgrep.rpm at this time $* Contains the3a string, openssh.rpm, w3m.rpm and webgrep.rpm. Input: [email protected] --shiyanSH]#VIMytest1 while[-N"$*" ] Doif[-D $1 ] ThenEcho "is a directory"Else Echo "$ is a file"fiShift Doneoutput: correct satisfaction [[email protected] --shiyanSH]#./mytest1awk  forFrsedselawkis a directory foris afileFR is afilesedIs a directorysel is afile

Shell's scripting Exercises