Is the programming language C used for any commercial projects?
Being a recent comp science graduate, I'm currently looking for work as an entry level programmer. I am noticing most of the job availabilities require knowledge of languages like C++, C#/VB, Java, Python, Ruby on Rails, etc...I have yet to come across anything requiring knowledge of C...and C was the first programming class I took that built the foundation for all the other languages I learned. I actually have a personal attachment to it and have always done my own extracurricular projects and experiments using C.
Is this language actually used in the workforce, or is it for generally for hobbies at home and creating your own fun projects on your own time? If not...what popular programs (or well known companies) utilize C?
Finally, what language should I become proficient in to be marketable to anyone? It seems like each company has their own specific language of choice, and it would be hard to be proficient in ALL the languages.