OK, there's a few concepts you'd need to get to grips with in order to write a solution to this problem. You've not said what shell or platform you're using, so I'm going to assume you're using Bash on Linux here, as that's probably the most likely possibility.
Firstly: knowing how many parameters a script has passed to it. This is actually fairly straightforward, and is handled by the Bash built-in variable $#. Take a look at this one-line example script, and try running it with different numbers of arguments. You should soon get a feel for how this works.
Next, testing things. There will be times (such as in your problem statement here) when you need to know how many arguments there are, or if they're equivalent to each other. Bash has a few ways of doing this, the simplest and most straightforward for your purposes being the if statement.
For instance, try running this second small example script with different numbers of arguments. Take particular note of what happens if you run it with three arguments.
Here, we're checking to see if the number of arguments ($#) is equal (==) to the number 3. If it is, we display a special message. If it's anything other than three (in other words, if it's something else), we display another message instead.
Now, Bash can test for all kinds of things besides whether one thing is equal to another thing. Of particular interest to you should be the conditional tests it can carry out to check if something is a file, or a directory, or if it exists, and so on. If you look at the man page for Bash in the "CONDITIONAL EXPRESSIONS" section, you'll find a whole list of these.
For example, if I wanted to check to see if the second argument passed to my script actually existed on the filesystem, I could do something like this.
Here, we check to see if the second argument ($2) exists (the meaning of the -e conditional expression). If it does, we print a message, and run the command /bin/ls -ld on it.
The last thing you'll probably need to understand to fully solve this problem is that conditional expressions (and plenty else besides) can be chained together using logic such that at least one of them must be true, or that they all must be true. Take a look at the "Compound Commands" section of the Bash man page to read how they all work.
I'll leave you with one last example though of a situation where we want to check that two particular things are the case at the same time.
Here, if the first argument ($1) and (the meaning of && here) the second argument ($2) are equal to "dog" and "cat" respectively, we print a special message. If they're not both set to exactly those things (and they both must be, due to our use of && here) then we print another message instead.
Anyway, hope all this helps give you some pointers on how to get started, and which documentation is best to look at to familiarise yourself with the Bash tests you'll need to know about.
Can some one smart here help I need to create a shell script that does this below using vi editor.
decrypts a file (specified as an argument to the script) containing text which was encrypted using the ROT-13 algorithm. The decrypted text should be written to a new file leaving the input file... (1 Reply)
I have an assignment in my programming class to write a shell script that will use command line parameters, display the # of parameters, display all parameters on the command line and display the parameters $0-$9. I understand some of the code (I will be using 'n' to represent the count through... (1 Reply)
I'm trying to write a history feature to a very simple UNIX shell that will list the last 10 commands used when control-c is pressed. A user can then run a previous command by typing r x, where x is the first letter of the command. I'm having quite a bit of trouble figuring out what I need to do, I... (2 Replies)
Im trying to create a script to archive specified directories into a specified tarball backup file. This is what i want the input to look like
ex. save -i '/bin/b*' -i '/bin/ls' -o backup
this is what i have
#!/bin/bash
#save - backup file script
unset myInput
unset myOutput
while... (3 Replies)
Hi,
I am new to unix and using linux 7.2. I would like to create a script that would make it easyer for me to run my java programms. At the moment I have to type java myJavaprogram
I am trying to write a script that will allow me to type something like this "myscript myJavaprogram" or maybe... (4 Replies)
Hi, I'm new to UNIX shell programming... can anyone help in doing the following :
1) create a text file named "Model File" having following columns :
Name Number Physics Chemistry
2) prompt user to n rows enter the name, number, physics ,chemistry
3) display the entire columns and rows... (1 Reply)
Hi,
I need help urgently for following issue. Pls help me to resolve this issue.
I am calling sql script file(file1.sql) from UNIX Shell Script(script1.ksh) using sql plus and trying to create flat file that contains all records returned from SQL query in SQL script(file1.sql)
I given... (6 Replies)
please help me to execute a simple shell script like
for i in `ls
echo $i
done
. i dont want to create a new sh file to execute it. Can i just type and execute it ? because I always this kind of simple for loops .
Please help .
Thanks (7 Replies)
Hi all,
I have a PLSQL script which has a IN list where it takes some ids as input. For example
SELECT * FROM EMPLOYEE WHERE EMPLOYEE_ID IN (comma separated list )
I want to run this quest inside a shell script but I would like to prepare the IN list dynamically where the employee ids... (1 Reply)
Hello everybody,
:wall:I am new to Linux and I want to create a simple script on Ubuntu that will allow to make database with a few perimeters.
create file and name it Database and complete it with any information
id firstname lastname phone
0
1
2
3
4
... (4 Replies)