Running Linux, 5th Edition - Matthias Kalle Dalheimer [414]
papaya$ diff -cr hello.old hello > hello.patch
Now, let's move to the system where the software needs to be updated. Assuming that the original source is contained in the directory hello, you can apply the patch with
papaya$ patch -p0 < hello.patch
The -p0 switch tells patch to preserve the pathnames of files to be updated (so that it knows to look in the hello directory for the source). If you have the source to be patched saved in a directory named differently from that given in the patch file, you may need to use the -p option without a number. See the patch(1) manual page for details about this.
Indenting Code
If you're terrible at indenting code and find the idea of an editor that automatically indents code for you on the fly a bit annoying, you can use the indent program to pretty-print your code after you're done writing it. indent is a smart C-code formatter, featuring many options that allow you to specify just what kind of indentation style you wish to use.
Take this terribly formatted source:
double fact (double n) { if (n= =1) return 1;
else return (n*fact(n-1)); }
int main () {
printf("Factorial 5 is %f.\n",fact(5));
printf("Factorial 10 is %f.\n",fact(10)); exit (0); }
Running indent on this source produces the following relatively beautiful code:
#include double fact (double n) { if (n = = 1) return 1; else return (n * fact (n - 1)); } void main () { printf ("Factorial 5 is %f.\n", fact (5)); printf ("Factorial 10 is %f.\n", fact (10)); exit (0); } Not only are lines indented well, but also whitespace is added around operators and function parameters to make them more readable. There are many ways to specify how the output of indent will look; if you're not fond of this particular indentation style, indent can accommodate you. indent can also produce troff code from a source file, suitable for printing or for inclusion in a technical document. This code will have such nice features as italicized comments, boldfaced keywords, and so on. Using a command such as: papaya$ indent -troff importrtf.c | groff -mindent produces troff code and formats it with groff. Finally, indent can be used as a simple debugging tool. If you have put a } in the wrong place, running your program through indent will show you what the computer thinks the block structure is. * * * [*] Always a possibility where this author's code is concerned! [*] The use of CVS has burgeoned along with the number of free software projects developed over the Internet by people on different continents. [*] The output shown here is from the last version that Larry Wall has released, Version 2.1. If you have a newer version of patch, you will need the -- verbose flag to get the same output. Using Perl Perl may well be the best thing to happen to the Unix programming environment in years; it is worth the price of admission to Linux alone.[*] Perl is a text- and file-manipulation language, originally intended to scan large amounts of text, process it, and produce nicely formatted reports from that data. However, as Perl has matured, it has developed into an all-purpose scripting language capable of doing everything from managing processes to communicating via TCP/IP over a network. Perl is free software originally developed by Larry Wall, the Unix guru who brought us the rn newsreader and various popular tools, such as patch. Today it is maintained by Larry and a group of volunteers. At the fime of writing, a major effort was underway to create a new, cleaner, more efficient version of Perl , Version 6. Perl's main strength is that it incorporates the most widely used features of other powerful languages, such as C, sed, awk, and various shells, into a single interpreted script language. In the past, performing a complicated job required juggling