Detailed description of inux bash built-in commands

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• Detailed description of inux bash built-in commands

Detailed description of inux bash built-in commands

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Solaris 10 System Management chapter 1 Solaris 10 scheduling system tasks. This chapter introduces the shell built-in commands and Unix Command list of Solaris 10. Due to the limited length, the appendix of this book is downloaded from www.broadview.com.cn. Since there are many Solaris system commands that cannot be described one by one, you can refer to Sun's man manual. This section describes the built-in bash commands.

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Main shell built-in commands

Shell has many built-inSource code. These commands are built in, so shell does not have to search for them on disk, so the execution speed is faster. Different built-in shell commands are different.

A.2.1 bash built-in commands

.: ExecuteProgram. Same as source.

. File: The dot command reads and executes the command from the file.

: NULL operation. The exit status is 0.

Alias: displays and creates aliases of existing commands.

BG: Put the job in the background.

BIND: displays the binding of the current keyword to the function, or binds the keyword to the Readline function or macro.

Break: jumps out of the innermost loop.

Builtin [sh-builtin [ARGs]: runs a built-in shell command, transmits parameters, and returns the exit status 0. This command is useful when a function has the same name as a built-in command.

CD [Arg]: Change the directory. If no parameter is included, return to the home directory. If the parameter is included, switch to the directory specified by the parameter.

Command Comand [Arg]: execute this command even if a function with the same name exists. That is, skip function search.

Declare [Var]: displays all variables, or declares variables with optional attributes.

Dirs: displays the directory of the current record (pushd results ).

Disown: delete an active job from the job table.

Echo [ARGs]: displays ARGs with a line break.

Enable: Enables or disables built-in shell commands.

Eval [ARGs]: Read ARGs into the shell and execute the generated command.

EXEC command: run the command to replace the current shell.

Exit [N]: Exit shell with status n.

Export [Var]: enables shell recognition of variables.

FC: A Historical modification command used to edit historical commands.

FG: place the background job to the foreground.

Getopts: parse and process command line options.

Hash: controls the internal hash table used to accelerate command search.

Help [command]: displays useful information about built-in commands. If a command is specified, the detailed information of the command is displayed.

History: displays the command history list with a line number.

Jobs: displays jobs placed in the background.

Kill [-signal process]: sends a signal to a process specified by the PID or job number. Enter kill-L to view the signal list.

Let: used to calculate the value of an arithmetic expression and assign the result of an arithmetic operation to a variable.

Local: Used in a function to restrict the scope of variables within the function.

Logout: log out from the shell.

Popd: delete an item from the directory stack.

Pushd: add an item to the directory stack.

PWD: print the current working directory.

Read [Var]: Read a row from the standard input and save it to the variable VAR.

Readonly [Var]: sets the variable VAR as read-only and cannot be reset.

Return [N]: Exit from the function. n is the exit status value specified for the return command.

Set: Set options and location parameters.

Shift [N]: shifts the position parameter n times left.

Stop PID: Pause the running of the PID process.

Suspend: Terminate the running of the Current Shell (it is invalid for the login shell ).

Test: checks the file type and calculates the conditional expression.

Times: displays the accumulated user time and system time of processes started by the current shell.

Trap [Arg] [N]: When the shell receives the signal n (n is 0, 1, 2, or 15), execute Arg.

Type [command]: displays the command type. For example, PWD is a built-in command of shell.

Typeset: Same as declare. Set variables and assign them attributes.

Ulimit: displays or sets the maximum number of available resources of a process.

Umask [octal number]: Creates a pattern mask for the owner, group, and other users of the User File.

Unalias: cancels all command alias settings.

Unset [name]: cancels the definition of the specified variable value or function.

Wait [pid # N]: Wait for the background process whose PID Number is n to end and report its end status.