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ORACLE Tutorials


Built-in Commands in Unix for the usage of Oracle


Built-in Commands
Built-in Commands are the commands that are built into a shell.they do not fork a new process when we execute them.The built-ins vary depending on the type of the shell. A brief listing of various built-ins is given below:

tcsh Built-ins :

type - gives the type of the command given as argument.For eg type cat will give the output as cat is hashed(/bin/cat)
read - Scripts can accept input from the user and store them in variables.
exec - executes a command.It has two main purposes:to run a command without creating a new process and to redirect a file descriptor -including standard input,output or error -of a shell script from within the script.
trap - catches a signal.A signal is a report to a process about a condition.Linux uses signals to report interrupts generated by users (eg : pressing a interrupy key),bad system calls,broken pipes,illegal instructions etc.Trap catches,one or more signals allowing us to direct the actions a script takes when it receives a specified signal.
kill - Aborts a process.the kill sends a signal to a process or a job.
getopts - Parses options.Parses command-line arguments,thereby making it easier to write programs that follow Linux argument conventions.

bash(Bourne Again shell) Builtins :

: - Returns 0 or true(null built-in)
.(dot) - Executes a shell script as a part of the current process
bg - Puts a suspended job in the background
break - Exits from a looping control structure
cd - Changes to another working directory
continue - Starts with the next iteration of looping control structure
echo - Displays its arguments
eval - scans and evaluates the command-line
exec - Executes a shell-script or a program in place of the current process
exit - Exits from te current shell.Same as CONTROL-D from an interactive shell.
export - Places the value of the variable in the calling environment.
fg - brings a job from the background into the foreground
getopts - Parses arguments to a shell script
jobs - Displays list of background jobs
kill - sends a signal to a process or job
pwd - displays the name of the working directory.Print working directory.
read - Reads a line from the standard input
readonly - declares a variable to be readonly
set - set shelflags or command-line argument variables,with no arguments,lists all variables.
shift - promotes each command-liargument
test - compares arguments
times - displays total times for the current shell and its children
trap - traps a signal
type - displays how eachrgument would be interpreted as a command
umask - returns the value of the file-creation mask
unset - Removes a variable or a function
wait - Waits for a bcakground process to terminate.

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