October 2024
Intermediate to advanced
272 pages
6h 54m
English
Content preview from Seven Obscure Languages in Seven Weeks
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Interacting with the System
m4 is a Turing-complete programming language, but many tasks are better left to specialized power tools. m4 designers allow you to utilize the services the host operating system provides.
The syscmd(cmd) macro executes the specified cmd—a program or a script with or without command-line options. The command may include pipes, I/O redirection, and even background execution. Anything permissible on the shell command line is permissible as an argument to syscmd. The macro displays the output of the cmd on the screen but doesn’t feed it into the m4 pipeline. For example, the following macro expands to an empty string and displays the number of files in the current working directory:
| | syscmd(ls | wc -l) |
| | dnl Output: ... |
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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