I am trying to write a script which will loop until a certain action has been performed. I have two files i would like to compares.
For example:
file1 has a list of user ids (about 900) from the company's e-mail server.
file2 has a list of user ids (about 50 or so) from /etc/passwd.
I have file1 in a array, I'd like to have file2 in a loop.
When the id matches it will be redirected the output to /dev/null ,
but when the two ids do not match, I need to redirected the output to file3. This is so I can delete user that have moved on.
This was my 1st try.
#!/usr/bin/ksh
set -A array file1
for i in ${array[@]}
do
echo "==== $i vs file2 ===="
diff $i file2
done > file3
In case you want to get the ksh script running, I'll comment on that. In your first try you were moving toward a solution where you repeatedly scanned a file. Don't do that. You want to read each file once. I think something like this will work:
i=0
exec < file1
while read array ; do
((i=i+1))
done
exec <file2
while read entry ; do
i=0
found=0
while ((i<${#array[@]})) ; do
if [[ $entry = ${array} ]] ; then
found=1
break
((i=i+1))
fi
done
if ((found)) ; then
echo $entry is in file1
else
echo $entry is not in file1
fi
done
You might get away with something like:
set -A array $(cat file1)
but the resulting set statement must be less than the max line length. It might work at first, then fail later. The loop seems a bit safer. And it fires up a cat process. So the loop will be a bit faster too.
i guess i don't know what it is. my thought of an array was a way to use multiple values for one variable name. well, I wanted to use your code of reading 2 files (lists) and using the variables on a conditional basis to print a message. (won't go any further, due to cross-posting).
ok, so in this part:
i=0
exec < file1
while read array ; do
((i=i+1))
done
you're reading the file in and looping.
My confusion is with this part:
exec <file2
while read entry ; do
i=0
found=0
while ((i<${#array[@]})) ; do
if [[ $entry = ${array} ]] ; then
found=1
break
((i=i+1))
fi
done
if ((found)) ; then
echo $entry is in file1
else
echo $entry is not in file1
fi
done
I assume that the found=0 is setting the count to zero? This line is the most confusing to me: while ((i<${#array[@]})) ; do
Are you saying do .. while "i" is less than the value of array[@]?
Thanks for any input.
puts two values in the array. I can see the first one with:
echo ${array[0]}
That [0] is called the subscript. Instead of a constant, it can be a variable.
echo ${array[i]}
will do different things depending on the value of i.
echo ${array[@]}
will echo all values (fred and barney in this case) in the array.
echo ${#array[@]}
will echo 2 since there are two elements in the array.
while (i<${#array[*]}))
in this case would loop until i is greater than or equal to two. Since i starts at zero, the loop will run twice with i at 0 and 1. Which is just right to examine each element of the array.
"found" is a flag, not a count. At first it is zero since we have not found what we are looking for. If we find it, found becomes one.
my thought of an array was a way to use multiple values for one variable name. well, I wanted to use your code of reading 2 files (lists) and using the variables on a conditional basis to print a message. (won't go any further, due to cross-posting).