UNIX for Dummies Questions & Answers

Greetings,

When directing in unix, symbol > means saving. E.g. I can save ls command output into mama like this:

ls -f > mama

Could someone give me a real example of how the opposite, i.e. symbol < is used?. Could not find its counterpart in Windows (I seem to learn better when i see unix's counterparts in windows upon which i depended for ages)

thanks
-a

more < some.txt
And that command works for me on Windows XP in a cmd window. On both XP and Unix I could have used:
more some.txt
but this is because the more command will process its arguments, find a filename, and open the file. Some commands, especially scripts that you may write may not have file opening code so they depend on being handed an opened file.

perderabo, thanks a lot, you're a good man...

The way i was taught about script files is to first make them executable with: chmod +x filename; then execute them with: ./ filename.

Does your statement about script mean that the < symbol can be used instead of the chmod + x, ./ commands?.

Thanks a bunch,
-a

Code:

## Read first line from file:
read line < FILENAME

If the line contained leading or trailing spaces, they would be lost with that command. To prevent that, the internal field separator is cleared:

Code:

IFS="" read line < FILENAME

If there are any backslashes in the line, they will be removed and the literal character following will be used. If the last character on the line is a backslash, read will continue reading the next line.

To disable backslash escaping, use the -r option:

Code:

IFS="" read -r line < FILENAME

To read an entire file (if the file is long, sed or awk may be a better tool to use):

Code:

while IFS="" read -r line
do
    ## Do something with the line here
done < FILENAME

The input of other commands can also be redirected from a file. For example, to change all uppercase As to Zs:

Code:

tr A Z < FILENAME

cfajohnson, thanks a lot for detailed explanation; i got the idea...