produce the same (Ecommerce web host) result if the current shell
produce the same result if the current shell is interactive: interactive On modern versions of UNIX both forms work equally well. On some older versions of UNIX the test -t command was not available, so the tty -s command had to be used. How do I discard the output of a command? Sometimes you will need to execute a command, but you don’t want the output displayed to the screen. In these cases you can discard the output by redirecting it to the file /dev/null: command > /dev/null Here command is the name of the command you want to execute. The file is a special file (called the bit bucket) that automatically discards all its input. To discard both output of a command and its error output, use standard redirection to redirect STDERR to STDOUT: command > /dev/null 2>&1 How can I display messages on STDERR? You can display a message on to STDERR by redirecting STDIN into STDERR as follows: echo message 1>&2 Here message is the message you want to display. If you are interested in shell functions that perform additional formatting please consult Chapter 21, “Problem Solving with Functions,” which covers several shell functions that display messages on to STDERR. How can I check whether a command was successful? A command is successful if it exits with a status of zero. A nonzero exit code indicates that an error has occurred. To check the exit code of the most recent command you executed, use the variable $?. For example: grep root /etc/passwd > /dev/null 2>&1 if [ $? -ne 0 ] ; then echo “No one is in charge!” ; fi Here you execute a grep command and then check the exit status of this command using the value stored in $?.
You need excellent and relaible webhost company to host your web applications? Then pay a visit to Inexpensive Web Hosting services.