UNIX System Programming

Source: csserver.evansville.edu
Topic: Shell Programming

Short Desciption:
UNIX System Programming Lecture 4 BASH Shell Programming BLP: Chapter 2 BABS Outline: Redirection ... zsh, ksh Change your default shell to bash $ chsh -s /bin/bash 2 Our First Shell Script A ...

 

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UNIX System Programming Lecture 4 BASH Shell Programming BLP: Chapter 2 BABS Outline: Redirection Shell Programming Introduction The shell is a command interpreter and a full- featured programming language.  It is especially well-suited for system administration and for file, directory and process management. Several different shells are available: sh, bash, csh, zsh, ksh Change your default shell to bash $ chsh -s /bin/bash 2 Our First Shell Script A hello world example $ cat > hello #! /bin/bash # Prompt user for name echo -n "Enter your name: " read name echo Hello there $name! exit 0 $ chmod +x hello $ . /hello Enter your name: Elmer Fudd Hello there Elmer Fudd! $ 3 Our First Shell Script Start with a sha-bang (#! ) .  The kernel will automatically pass the script to the proper interpreter.  End with ìexit 0î (or non-zero exit to indicate an error condition) . Comments begin with a # Make the script executable and run it like a standard program OR you can also run the program like this: $ bash hello# run in new env (like . /hello) $ . hello # run in same env (also source hello) 4 Wildcards (globbing) Wildcard expansion is done by the shell.  Not by the application. A * matches any character except a leading dot (. ) .  A ? matches any single character. $ echo * a. 1 b. 1 c. 1 t2. sh test1. txt $ ls t? . sh t2. sh $ ls [a-c]* a. 1  b. 1  c. 1 $ ls {b*, c*, *est*} b. 1  c. 1  test1. txt $ ls *. {1, sh} a. 1  b. 1  c. 1  t2. sh 5 Redirection Every program automatically has three files/streams available: standard input, standard output, and standard error. In C, the FILE* streams are stdin, stdout, and stderr. In C++, the IO streams are cin, cout, and cerr. By default, they are connected to the keyboard, the display, and the display but they can be redirected. 6 Redirection Heres ...

 

 

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