Csh the C Shell Check out my other tutorials on the Unix Page, and my Check my blog. Copyright 1. 99. 4, 1. Bruce Barnett and General Electric Company. Copyright 2. 00. 1, 2. Bruce Barnett. All rights reserved. You are allowed to print copies of this tutorial for your personal. Original version written in 1. Sun Observer. This section describes C Shell CSHTCSH programming. Example Programs In C Using Do While' title='Example Programs In C Using Do While' />It covers conditional testing, control loops, and other advanced techniques. This month begins a tutorial on the bad boy of UNIX, lowest of the low. Yes, I am talking. C shell. FAQs flame it. Experts have criticized it. Unfortunately, this puts UNIX novices in an awkward. Many people are given the C shell as their default shell. They arent familiar with it, but they have to learn. They need help, but get criticized every time they ask a question. Imagine the following conversation, initiated by a posting on USENET. Novice How do I do XYZ using the C shell Expert You shouldnt use the C shell. Use the Bourne shell. Novice I try to, but I get syntax errors. Expert Thats because you are using the C shell. Use the Bourne shell. Novice Ive now using the Bourne shell. How to I create aliases. Bourne shell Expert You cant. Novice I dont have these shells on all of the systems I use. Flatout 2 Iso. What can I use Expert In that case, use the C shell. Novice But you told me I shouldnt use the C shell Expert Well, if you have to, you can use the C shell. Its fine for interactive sessions. But you shouldnt use it for scripts. Novice Its really confusing trying to learn two shells. I dont know either shell very well, and. Im trying to learn. JUST enough to customize my environment. Id rather just learn one shell at a time. Expert Well, its your funeral. Novice How do I do XYZ using the C shell Another Expert You shouldnt be using the C shell. Use the Bourne shell. Novice The C shell does have problems. See My top 1. 0 reasons not to use the C shell. It is C programming FAQ code examples to Crack Interview. It has C language basic and simple source code by examples. It has arranged just like c tutorials with examples. Complete package that includes a machine simulation teaches the student the setup and operation of CNC machines. CNC program simulation and gcode debugger. Important Threshold Update Effective October 1, 2015, the Department of Defense DOD, General Services Administration GSA, and National Aeronautics. C s i, as in the letter c is a generalpurpose, imperative computer programming language, supporting structured programming, lexical variable scope and. WELCOME TO the Seventh Edition of Introduction to Programming Using Java, a free, online textbook on introductory programming, which uses Java. Some can be fixed. Some are unimportant now, but later on might cause grief. Ill mention these problems. But Ill let you decide. C shell, or start using the Bourne shell. Switching shells is difficult. Example Programs In C Using Do While' title='Example Programs In C Using Do While' />For a more recent example, consider the disturbingly cheerful pop song by Foster the People, Pumped Up Kicks, which deals with a school shooting. Origins What is the purpose of the project No major systems language has emerged in over a decade, but over that time the computing landscape has changed tremendously. If you want to use the C shell, thats fine. Ill show you the pitfalls, so you can intelligently decide. No pressure. You can switch at any time. But be aware that the C shell is seductive. It does have some advantages over the Bourne shell. But sometimes what seems like an advantage turns into a disadvantage later. Let me discuss them in detail. The first problem I faced with the C shell involved another language. I had a problem that required a. The C shell has a. The following command. C shell. echo This quote doesnt end. The Bourne shell would continue till the end of the script. This is a good feature for an interactive shell. But if you want to include a multi line string, such as an. C shell script, you will have problems. You can place a backslash at the end of each line. Using them inside a C shell script would require two backslashes in a row. There are some other strange quoting problems. Like the Bourne shell, the C shell has three ways to quote. You can use the single quote, double quote and backslash. But combine them, and find some strange combinations. You can put anything inside single quotes in a Bourne shell script. The C shell wont let you do that. You have to use a backslash if you want to do this. Also, the following. But in this case you cannot even use a backslash. The followings an error in the C shell. Unix shells have many special characters, and quoting them marks them as normal ASCII telling the shell not to interpret them. And this is true with every Unix shell there is, except the C shell. In the above cases, putting quotes around some characters. C shell, instead of. The second problem is subtle, but may be the next problem you. The Bourne shell has a true syntax parser the. Some pieces are commands. Other pieces are quoted strings. File redirection is handled the same way. Commands can be combined on one line, or span several lines. It doesnt matter. As an example, you can use. The parsing of file redirection is independent of the particular command. The following. is valid in the Bourne shell. The same holds true for other Bourne shell commands. Once you learn the principles, the behavior is predictable. The C shell does not have a true parser. Instead, the code executes one section for the. What works for one command may not work for another. C shell. There are two file redirections, and the C shell cant do either. Also, in the C shell, certain words. Therefore you might try something that works with one command. Ive reported a lot of bugs to Sun, and to their credit, many have been fixed. Try the same code on other systems, however, and you might get syntax errors. The parsing problem is also true with shell built in commands. Combine them, and. Try the following C shell sequence. There are other examples of this. These are the types of problems that sneak up on you when you. The Bourne shell has the. You cant do this with the C shell. The C shell seems to act on one line at a time and. Sometimes you have to ask a person for input in the middle of a script. Sometimes you have to read some information from a file. The Bourne shell allows you to specify the source of information. Even though a script is connected to a pipe, you can ask the user for input. The C shell does not have this flexibility. It has a mechanism to get a line from standard input, but that is all it can do. You cannot have a C shell script get input from both a file and the terminal. With respect to file redirection, the Bourne shell. C shell is very limited. With the Bourne shell, you can send standard error. You can discard standard output, but keep the error. You can close any file descriptor, save current ones, and restore them. The C shell cant do any of these steps. If you want to make your script more robust, you must add. That is, your script must terminate. The C shell has limited abilities. You can either do nothing, ignore all signals, or trap all signals. Its an all or nothing situation. The Bourne shell can trap particular signals, and call a special routine. You can retain the process ID of a background process. This allows you to relay signals received to other processes under your control. The C shell cannot do this. You can use the C shell for simple scripts. If you dont add many new features, and only write scripts for yourself. C shell may be fine for you. But it is a time bomb. There are many times. I wanted to add a new feature to a C shell script. Or else I tried to port a C shell script to a different system. Yes, you can use the C shell. Use it for as long as you want. Tick. Tick. Tick. This is my second tutorial on the C shell. This month, I will discuss. Like all shells, the C shell examines each line, and breaks it up into. The first word is a command, and additional words are. The command. more uses a meta character, the asterisk. The shell sees the asterisk, examines the current directory, and transforms. There are many other meta characters. Some are very subtle. Consider this meta character example. The meta character Its the space. In this case, the space indicates the end of one filename. The space, tab, and new line character are used by the C shell to. The Bourne shell allows more control, as any character can be. These meta characters are an integral part of UNIX. Or rather, an integral part. A meta character is simply a character with. The file system doesnt really care about meta characters.