# Command Line
Run `erlperf` with no arguments to get command line usage.
## Synopsis
```bash
erlperf [FLAG] runner [INIT] [INIT_RUNNER] [DONE] [runner...]
```
## Flags
| Short | Long | Description |
|-------|-------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| -c | --concurrency | Specifies the number of workers per job. Allowed only in continuous mode |
| | --cv | Coefficient of variation. Accepted in continuous and concurrency estimation mode. Benchmark keeps running until standard deviation is below the specified number |
| -i | --isolation | Requests to run every benchmark in a separate Erlang VM for isolation purposes |
| -s | --samples | Number of samples to take. Defaults to 1 for timed mode, 3 for continuous and concurrency estimation |
| -d | --sample_duration | Sample duration, in milliseconds, for continuous and concurrency estimation modes |
| -l | --loop | Sample duration (iterations) for the timed mode. Engages timed mode when specified |
| | --max | Maximum number of workers allowed in the concurrency estimation mode |
| | --min | Starting number of workers in concurrency estimation mode |
| -pa | | Adds extra code path to the Erlang VM. Useful for benchmarking *.beam files on your filesystem |
| -r | --report | Requests `basic`, `extended` or `full` report. Defaults to `basic` when less than 10 samples are requested, and `extended` for 10 and more |
| -q | -squeeze | Engages concurrency estimation mode |
| -t | -threshold | Sets number of extra workers to try in concurrency estimation mode before concluding the test |
| -v | --verbose | Turns on verbose mode, including generated source code, VM statistics and performance of continuous jobs) |
| -w | --warmup | Warmup |
## Benchmark code
At least one runner code is required. Specify multiple runner codes to perform
a comparison run.
Initialisation and cleanup definitions are read in the same order as runner codes. Example:
```bash
# first runner receives 1 as input, second - 2
erlperf --init_runner '1.' 'run(1) -> ok.' 'run(2) -> ok.' --init_runner '2.'
# next run fails with function_clause, because first runner receives '2', and second - 1
erlperf --init_runner '2.' 'run(1) -> ok.' 'run(2) -> ok.' --init_runner '1.'
```
| | Description |
|-------------------|---------------------------------------------------------------------------|
| --init | Job initialisation code, see accepted callable formats below |
| --init_runner | Worker initialisation code |
| --done | Job cleanup code |
| | |
| --init_all | Default init code for all runners that do not have a specific code |
| --init_runner_all | Default init_runner code |
| --done_all | Default done code |
Accepted callable formats:
* valid Erlang code: `timer:sleep(1).`
* valid Erlang function: `run() -> timer:sleep(1).`
* function with arguments: `run(X) -> timer:sleep(X).', 'run(X, Y) -> timer:sleep(X), Y.`
* tuple with module, function name and arguments: `{timer, sleep, [1]}`
* file name with call chain recording: `record.trace`. **deprecated**, do not use
