查看“沙盒”的源代码

3.1.1 Shell Operation

The following is a brief description of the shell’s operation when it reads and executes a command. Basically, the shell does the following: 

# Reads its input from a file (see Shell Scripts), from a string supplied as an argument to the -c invocation option (see Invoking Bash), or from the user’s terminal. 
# Breaks the input into words and operators, obeying the quoting rules described in Quoting. These tokens are separated by metacharacters. Alias expansion is performed by this step (see Aliases). 
# Parses the tokens into simple and compound commands (see Shell Commands). 
# Performs the various shell expansions (see Shell Expansions), breaking the expanded tokens into lists of filenames (see Filename Expansion) and commands and arguments. 
# Performs any necessary redirections (see Redirections) and removes the redirection operators and their operands from the argument list. 
# Executes the command (see Executing Commands). 
# Optionally waits for the command to complete and collects its exit status (see Exit Status).