percent

% in shell context typically refers to job control, bringing background

TLDR

Bring most recent background job to foreground

$ %

Bring job number N to foreground

$ %[N]

Bring job starting with string to foreground

$ %[string]

Bring job containing string to foreground

$ %?[string]

Use modulo operator in arithmetic

$ echo $((10 % 3))

% in shell context typically refers to job control, bringing background jobs to the foreground. It's shorthand for the fg command.
When a command is suspended (Ctrl+Z) or run in background (&), it gets a job number. The % notation provides quick access to these jobs.
In arithmetic contexts $(( )), % is the modulo operator, returning the remainder of integer division.
In prompt strings (PS1), % introduces escape sequences in zsh for dynamic prompt elements.

JOB SPECIFICATIONS

% or %+ or %%

Current (most recent) job

Previous job

Job number n

%string

Job whose command starts with string

%?string

Job whose command contains string

Start background job

sleep 100 &

[1] 12345

Bring to foreground

In arithmetic

remainder=$((17 % 5)) # Result: 2

In zsh prompt (show current directory)

PS1='%~ $ '

$
# CAVEATS

Job control requires an interactive shell. Not available in scripts by default.

The **%** interpretation is context-dependent: job control at command position, modulo in arithmetic, format specifier in strings.

Job numbers reset when the shell restarts.

# SEE ALSO

fg(1), bg(1), jobs(1), kill(1)