Conditional AND List

A conditional AND list is a sequence of one or more pipelines separated by the && control operator. It enforces short-circuit left-to-right evaluation, where a subsequent command is executed if and only if the preceding command terminates with an exit status of zero (success).

Syntax

pipeline1 && pipeline2 [&& pipeline3 ...]

Execution Mechanics

1. The shell evaluates pipeline1 and waits for it to terminate.
2. If pipeline1 yields an exit status of 0, the shell proceeds to evaluate pipeline2.
3. If pipeline1 yields a non-zero exit status, the shell immediately aborts evaluation of the list. pipeline2 and any subsequent pipelines are not executed.
4. This sequential evaluation continues until a pipeline returns a non-zero status or the end of the list is reached.

Exit Status The overall exit status of an AND list is the exact exit status of the last command executed within that list.

• If the list short-circuits due to a failure, the exit status of the list is the non-zero value of the pipeline that failed.
• If the entire list executes successfully, the exit status of the list is 0 (the exit status of the final pipeline).

Precedence and Associativity The && control operator shares equal precedence with the conditional OR operator (||). When combined in a single compound list without explicit grouping, they are evaluated with strict left-to-right associativity. To alter the evaluation order, pipelines must be enclosed in grouping constructs, such as a subshell ( ... ) or a current-shell group { ...; }.

# Left-to-right associativity
pipeline1 && pipeline2 || pipeline3


# Altered precedence using a current-shell group
pipeline1 && { pipeline2 || pipeline3; }

Asynchronous Execution If an AND list is terminated by the asynchronous control operator &, the entire list is executed in the background as a single subshell process. The short-circuit logic remains intact within that background process.

pipeline1 && pipeline2 &

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