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Full Discussion: Understanding Xargs
Top Forums Shell Programming and Scripting Understanding Xargs Post 303010124 by RudiC on Wednesday 27th of December 2017 05:24:23 AM
Old 12-27-2017
Now, these are very basic questions from quite broad a range of IT, and I'm not sure I can cover that to satisfaction. On top, there may be a language barrier, e.g with "occurrence". I'd advise to use a dictionary, as - to me - the meaning got immediately clear when seeing the translations. Please also consult introductory text books and / or man pages.

It might be worthwhile to internalize the concept of a string which you will encounter everywhere in IT (tools, databases, documents, files, ...) when needing to represent text. It can come in a variety of shapes, like fixed or varying length strings, zero terminated or with a leading length indicator, string constants, substrings, string concatenations, and what have you, and there are many tools, libraries, functions to handle them. Different digital items (numbers, logical values) can be output to screen as readable text representations only, not as the individual items themselves.

Then, there are text files, a loosely structured collection of (mostly) printable characters. In *nix systems, those consist of lines of characters terminated by a <new line> (\n, ^J, 0x0A) character. But this is not the only possible text representation. When reading a line from a file, you can put it into a single string variable, or split it into several substrings. If you do so by applying spaces and / or punctuation chars for separating, the substrings will be words. But any other separation is possible albeit not necessarily sensible. So, a line is sort of a superset of (a group of) strings.

A "command line" specifies a collection of a command name (perhaps including a path), zero or more options (with possible arguments), and zero or more parameters. Any of those is a (possibly one character) string, analysed by the command interpreter, and then supplied to the program being executed. Please be aware that the terms "argument" and "parameter" are not strictly distinguished between and both are loosely and interchangably used. (I neglected possible local variable assingments and redirections to avoid overcomplicaton.)

Last edited by RudiC; 12-27-2017 at 10:13 AM.. Reason: Some typos
 

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lorder(1)						      General Commands Manual							 lorder(1)

NAME
lorder - Finds the best order for member files in an object library SYNOPSIS
lorder file... DESCRIPTION
The lorder command is essentially obsolete. Use the following command in its place: % ar -ts file.a The lorder command reads one or more object or library archive files, looks for external references, and writes a list of paired filenames to standard output. The first of each pair of files contains references to identifiers that are defined in the second file. You can send this list to the tsort command to find an ordering of a library member file suitable for 1-pass access by ld. If object files do not end with lorder overlooks them and attributes their global symbols and references to some other file. EXAMPLES
To create a subroutine library, enter: lorder charin.o scanfld.o scan.o scanln.o | tsort | xargs ar qv libsubs.a (Enter this command entirely on one line, not on two lines as shown above.) This creates a subroutine library named libsubs.a that contains charin.o, scanfld.o, scan.o, and scanln.o. The ordering of the object mod- ules in the library is important. The lorder and tsort commands together add the subroutines to the library in the proper order. Suppose that scan.o calls entry points in scanfld.o and scanln.o. scanfld.o also calls entry points in charin.o. First, the lorder command creates a list of pairs that shows these dependencies: charin.o charin.o scanfld.o scanfld.o scan.o scan.o scanln.o scanln.o scanfld.o charin.o scanln.o charin.o scan.o scanfld.o This list is piped to the tsort command, which converts the list into the ordering that is needed: scan.o scanfld.o scanln.o charin.o Note that each module precedes the module it calls. charin.o, which does not call another module, is last. The second list is then piped to xargs, which constructs and runs the following ar command: ar qv libsubs.a scan.o scanfld.o scanln.o charin.o This ar command creates the properly ordered library. FILES
Temporary files SEE ALSO
Commands: ar(1), as(1), cc(1), ld(1), make(1), nm(1), size(1), strip(1), tsort(1), xargs(1) Files: a.out(4), ar(4) lorder(1)
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