picca/man/picca.1.md

% PICCA(1) Version <VERSION> | User Commands
% Written by Bryson Steck (bryson@steck.dev)
% August 2025

# NAME

picca - a Parallel Implementation of Common Checksum Algorithms

# SYNOPSIS

picca [_OPTIONS_] [_FILE_]...

# DESCRIPTION

Print or verify checksums by reading files in parallel, using the SHA256 algorithm by default.

When conditions are suitable, being able to hash multiple files in parallel can significantly increase performance with multi-file hashing operations. However, it can also significantly degrade performance depending on different factors with your particular system. Some factors to consider are:

- The type of storage being used,
- The type of processor(s) in the system,
- The latency of I/O operations,
- etc.

# OPTIONS

With no FILE(s) specified, or when FILE is a dash (-), picca will read from standard input.

**-a, &ndash;&ndash;algorithm** _ALGORITHM_
: Specify the algorithm for hashing. The default value is sha256. A list of supported algorithms can be found in the **ALGORITHMS** section.

**-c, &ndash;&ndash;check** _CHECK_
: Read checksums from the specified file and verify them. This argument can be specified multiple times to read checksums from multiple files.

**-d, &ndash;&ndash;debug**
: Enable debug output for troubleshooting purposes. Messages output to standard error.

**-f, &ndash;&ndash;canonicalize**
: Show canonicalized file paths; convert relative paths to absolute paths.

**-h, &ndash;&ndash;help**
: Show command usage and available options

**-t, &ndash;&ndash;threads** _THREADS_
: Use at most, at any given time, this number of threads. By default, picca will detect the amount of processors on the system and use that as the thread count. Using 0 for this value results in the default behavior; this is the same as omitting this option.

**-V, &ndash;&ndash;version**
: Show the version of picca and exit

The following option is only useful when verifying checksums with the **-c** flag:

**-q, &ndash;&ndash;quiet**
: Only print checksums that fail verification; do not print anything to standard output if a verfication is successful. Helpful to limit the amount of information printed to the screen.

# REPORTING BUGS

Bugs to the picca project can be submitted via an issue on Codeberg: https://codeberg.org/bryson/picca

# SEE ALSO

The main repository is located at https://codeberg.org/bryson/picca.

A read-only mirror is available at https://forge.steck.dev/bryson/picca.

Container images for use with Docker are available at https://forge.steck.dev/bryson/-/packages/container/picca.

# COPYRIGHT

Copyright &copy; 2025 Bryson Steck.

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.