The vocabulary of shell command language
The following sections list metacharacters, special characters, input
and output redirection, variables, and process control.
Special characters in the shell
* ? [ ]
Metacharacters; used to provide a shortcut to referencing filenames,
through pattern matching.
Executes commands in the background mode.
Sequentially executes several commands typed on one line,
each pair separated by ;.
Turns off the meaning of the immediately following special character.
Enclosing single quotes turn off the special meaning of all characters
except single quotes.
Enclosing double quotes turn off the special meaning of all characters
except $, single quotes, and double quotes.
Redirecting input and output
Redirects the contents of a file into a command.
Redirects the output of a command into a new file,
or replaces the contents of an
existing file with the output.
Redirects the output of a command so that it is appended
to the end of a file.
Directs the output of one command so that it becomes
the input of the next command.
Substitutes the output of the enclosed command in place of `command`.
Executing and terminating processes
Submits the following commands to be processed
at a time when the system load
is at an acceptable level.
ends the batch command.
Submits the following commands to be
executed at a specified time.
ends the at command.
Reports which jobs are currently in the at
or batch queue.
Removes the at or batch job from the queue.
Reports the status of the shell processes.
Terminates the shell process with the specified process ID (PID).
nohup command list &
Continues background processes after logging out.
Making a file accessible to the shell
chmod u+x filename
Gives the user permission to execute the file (useful for shell program files).
mv filename $HOME/bin/filename
Moves your file to the bin directory
in your home directory.
This bin holds executable
shell programs that you want to be accessible.
Make sure the PATH variable
in your .profile file
specifies this bin.
If it does,
the shell will search in $HOME/bin
for your file when you try to execute it.
If your PATH variable does not
include your bin,
the shell will not know where to find
your file and your attempt to execute it
The name of a file that contains a shell program
becomes the command that you type to run that shell program.
A numbered variable used within a shell program to reference values automatically assigned by the shell from the arguments of the command line invoking the shell program.
A command used to print the value
of a variable on your terminal.
A special parameter that contains the number of arguments with which the shell program has been executed.
A special parameter that contains the values of all arguments with which the shell program has been executed.
A variable to which the user can give a name
and assign values.
Variables used in the system
Denotes your home directory;
the default variable for the cd command.
Defines the path
your login shell follows to find commands.
Gives the name of the file
containing your electronic mail.
Defines the primary
and secondary prompt strings, respectively.
Defines the type of terminal.
Login name of the user.
Defines the internal field separators (normally the space, the tab, and the carriage return).
Allows you to request that the curses
and terminfo subroutines
search a specified directory tree
before searching the default directory
for your terminal type.
Sets and maintains the local time zone.
Shell programming constructs
Summary of shell command language
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UnixWare 7 Release 7.1.4 - 27 April 2004