Shell Programming and Scripting

Q1>How do i read and write to file in shell script. Here is what i want let's assume the filename as "file1"

Read file1

Check the content of file1 which can be either "0" or "1"

if(content == 0)
{
execute a command
}

flush file1(remove all contents in it)

write "1" in to file1

execute a few commands

flush file1(remove all contents in it)

write "0" in to the file

Q2>How do i store the result of a shell script command in a variable.For example

"dropdb something" - When i execute this command on bash it gives a message
"database dropped" how do i capture this in shell and store it in a variable and compare it

Thanks for helping me!

Answer for question number 2,

you can save the variable by usning "tee" command or redirect options..

1. command | tee

2. 2>&1 ( redirect stdout and stderr )

So in my case the command is "dropdb" so will it be

"dropdb | tee"

But how do i store the outcome of the command in a var.

& i did not get the second option 2>&1 ( redirect stdout and stderr ) can u explain it to me with an example please

try this

1. "dropdb | tee file_name"


2. dropdb > /home/sir/file_name 2>&1

#Here stand error and stand out get sent to the o/p file i.e. file_name

in both the cases message will be stored in file_name.

then you can processes it forther..

Is there any way i can transfer the output of a command to a variable.?

cat(print) the file and assign it to variable

Variable=`cat file_name`