The single square braces,, are the traditional Bash symbols that are equivalent to the test command: if test arg1 operator arg2 then list The spaces in the comparison are required as shown. The functional syntax of these comparison operators is one or two arguments with an operator that are placed within square braces, followed by a list of program statements that are executed if the condition is true, and an optional list of program statements if the condition is false: if then list Each operator returns true (0) if the condition is met and false (1) if the condition is not met. There are three types of operators: file, numeric, and non-numeric operators. The most basic form of the if control structure tests for a condition and then executes a list of program statements if the condition is true. Logical operatorsīash has a large set of logical operators that can be used in conditional expressions. Logical operators are the basis for making decisions in a program and executing different sets of instructions based on those decisions. The third and final article in the series will explore the for, while, and until loops that enable repetitive operations. This second article looks into the types of file, string, numeric, and miscellaneous logical operators that provide execution-flow control logic and different types of shell expansions in Bash. The first article explored some simple command-line programming with Bash, including using variables and control operators. This three-part series (which is based on my three-volume Linux self-study course) explores using Bash as a programming language on the command-line interface (CLI). Welcome to the communityīash is a powerful programming language, one perfectly designed for use on the command line and in shell scripts.
0 kommentar(er)
