# C shell

> Unix shell

**Wikidata**: [Q1064516](https://www.wikidata.org/wiki/Q1064516)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/C_shell)  
**Source**: https://4ort.xyz/entity/c-shell

## Summary
The C shell (csh) is a Unix shell developed by American computer scientist Bill Joy in 1978. It is a command-line interpreter for Unix-like operating systems, particularly BSD, and is classified as a programming language and free software distributed under the 3-clause BSD License. The C shell was succeeded by tcsh, an enhanced but compatible version.

## Key Facts
- Developed by Bill Joy in 1978.
- A Unix shell and command-line interface language.
- Distributed as free software under the 3-clause BSD License.
- Runs on BSD-based Unix-like operating systems.
- Succeeded by tcsh, an enhanced version of the C shell.
- Aliases include csh, tcsh, csh.1, csh(1), and C 쉘.
- Media type: application/x-csh.
- Short name: csh.
- Influenced by GNU Bash, a GNU Project implementation of the standard Unix shell.
- Available as a package on Ubuntu, Debian, and FreeBSD.
- Source code repositories include NetBSD and OpenBSD.
- Copyrighted software with a free software directory entry.

## FAQs
**What is the C shell, and who developed it?**
The C shell (csh) is a Unix shell developed by Bill Joy in 1978. It is a command-line interpreter for Unix-like systems, particularly BSD, and is distributed as free software.

**What license does the C shell use?**
The C shell is distributed under the 3-clause BSD License, a permissive free software license compatible with the GNU GPL.

**What operating systems does the C shell run on?**
The C shell runs on BSD-based Unix-like operating systems, as indicated by its classification.

**What is the relationship between the C shell and tcsh?**
The C shell was succeeded by tcsh, an enhanced but compatible version of the C shell developed by the same creator, Bill Joy.

**Where can I find the source code for the C shell?**
The source code for the C shell is available in repositories maintained by NetBSD and OpenBSD.

## Why It Matters
The C shell played a significant role in the evolution of Unix shells by introducing features that influenced later implementations, including tcsh. As a free software project, it adheres to principles of user freedom, allowing users to run, study, change, and distribute it. Its development by Bill Joy, a prominent figure in computer science, underscores its importance in the Unix ecosystem. The C shell's compatibility with BSD systems and its permissive licensing further cemented its place in Unix history.

## Notable For
- One of the earliest Unix shells developed by Bill Joy.
- Influenced by GNU Bash, another major Unix shell.
- Available as a package on major Linux distributions like Ubuntu and Debian.
- Maintained in source code repositories by NetBSD and OpenBSD.
- Distributed under the 3-clause BSD License, ensuring broad compatibility.

## Body
### History
The C shell was developed by Bill Joy in 1978, making it one of the earliest Unix shells. It was created as part of the BSD Unix distribution, reflecting its close association with BSD-based systems. The C shell was succeeded by tcsh, an enhanced version developed by the same creator, which remains compatible with the original C shell.

### Development and Licensing
Bill Joy, an American computer scientist, engineer, programmer, and businessperson, developed the C shell. The project is distributed under the 3-clause BSD License, a permissive free software license that allows users to freely run, study, change, and distribute the software. This licensing model ensures broad compatibility and adherence to free software principles.

### Technical Specifications
The C shell is classified as a programming language and a command-line interface language. It has aliases such as csh, tcsh, csh.1, csh(1), and C 쉘. The media type for C shell scripts is application/x-csh. The short name for the C shell is csh. The C shell is influenced by GNU Bash, a GNU Project implementation of the standard Unix shell, which was first released in 1989.

### Availability and Distribution
The C shell is available as a package on Ubuntu, Debian, and FreeBSD. The source code is maintained in repositories by NetBSD and OpenBSD. The C shell has a free software directory entry, indicating its status as free software. The C shell is copyrighted, with its source code available under the terms of the 3-clause BSD License.

### Influence and Legacy
The C shell's development by Bill Joy and its influence on later shells like tcsh highlight its importance in Unix history. Its permissive licensing and compatibility with BSD systems ensure its continued relevance in the Unix ecosystem. The C shell's availability on major distributions and its presence in free software directories underscore its enduring impact.

## References

1. [tcsh-6.19.00 – extended C-shell with many useful features (Canadian English)](http://openbsd.su/ports/shells/tcsh)
2. [NetBSD](http://bxr.su/n/bin/csh/csh.c)
3. [OpenBSD](http://bxr.su/o/bin/csh/csh.c)
4. Freebase Data Dumps. 2013
5. Encyclopedia of graphics file formats
6. [FreeBSD](http://bxr.su/f/bin/csh/Makefile)
7. [DragonFly BSD](http://bxr.su/d/bin/csh/Makefile)
8. Quora