Shell Programming and Scripting

Code:

if [ $USER != webadmin ]; then
        echo 1>&2 Info : Only webadmin user can execute this script. please login and webadmin.
        exit 127
fi

if [ $# -ne 1 ]; then
        echo 1>&2 Usage: $0 *.file-extention
        echo 1>&2 e.g: $0 *.war
        exit 127
fi

I want to know what the "echo 1>&2" means
also what "if [ $# -ne 1 ]; then" means

thanks

echo 1>&2 - sent this msg to stderr pipe
$# -ne 1 - find the number of arguments available whilst execution

Code:

Normally:
echo 2>&1
rather than
echo 1>&2

Hi.
When a program runs, 3 files are made available: STDIN (0), STDOUT (1), and STDERR (2), all assigned to the terminal.

Often programs are connected together into pipelines, where the STDOUT of a program is connected to the STDIN of another program. If a program were to write an error message to STDOUT, it could be swallowed down the pipeline. Consequently,a good practice is to specify that error messages be written to STDERR.

If we were to write :

Code:

echo " Error!" >2

the message would be written on file "2". So the shell uses the convention that "&2" will be whatever STDERR is assigned to. So we write:

Code:

echo " Error!" >&2

Because STDERR is normally assigned to the terminal, the user is likely to notice it. (The "1" in "1>&2" is understood, and may be omitted.)

The placement of "1>&2" can be anywhere where it is directly exposed to the shell:

Code:

>&2 echo One
echo >&2 Two
echo Three >&2

but I have seen it in most situations at the end of the statement.

Best wishes ... cheers, drl