What does $$ mean in bash Meaning and Definition

Pronunciation

/ˈdɒlərˌsɪɡn/ 🔊

Part of Speech

Symbol

Definition

In bash, $$ is a special variable that represents the process ID of the current shell. It is often used in scripts and commands to refer to the current shell or process.

Examples

1. “The $$ variable is used to capture the process ID of the current shell.”

2. “You can use $$ to get the current process ID in a bash script.”

Synonyms

1. $BASHPID

2. $pid

Antonyms

None

Additional Information

The $$ variable is a built-in bash variable that is automatically set to the process ID of the current shell. It is commonly used in scripts and commands to refer to the current shell or process. For example, you can use $$ to get the current process ID and use it to kill the process or to get information about the process.

In bash, $$ is also used to get the process ID of the current shell in a subshell. For example, you can use $$ to get the process ID of the current shell in a subshell and use it to kill the subshell.

It’s worth noting that $$ is not the same as $$. $$ is the process ID of the current shell, while $$ is the process ID of the last command executed in the shell.

Etymology

The $$ variable has its roots in the early days of Unix, where it was used to represent the process ID of the current shell. The variable was later adopted by bash and other shells, and has since become a standard feature of Unix-like operating systems.

Usage Notes

When using $$ in a script or command, make sure to use it correctly. For example, you can use $$ to get the current process ID and use it to kill the process, but you should not use $$ to get the process ID of a subshell.

Also, note that $$ is not the same as $$. $$ is the process ID of the current shell, while $$ is the process ID of the last command executed in the shell.

Cultural References

The $$ variable has been referenced in various forms of media, including books, articles, and online forums. It is often used as a symbol of Unix-like operating systems and is commonly used by system administrators and programmers.

Idiomatic Expressions or Phrases

None

Related Words or Phrases

1. $BASHPID

2. $pid

Collocations

1. “The $$ variable is used to capture the process ID of the current shell.”

2. “You can use $$ to get the current process ID in a bash script.”

Frequency of Use

The $$ variable is commonly used in bash scripts and commands, particularly in Unix-like operating systems. It is often used by system administrators and programmers to refer to the current shell or process.

Common Misspellings

1. $$$

2. $$