3 - Object Names in Linux

Object Names in Linux

File names can contain any characters other than forward slash ( / ),they are reserved for the "root dir".

File names use alphanumeric characters,underscores, hyphens and periods only. Other characters, such as dollar signs, percentage signs and brackets, have special meanings to the shell so we should avoid using them in out file names.File names should never begin with a hyphens.

Reserved characters and words

slash (/) -used as a path name component separator;

question mark (?) -used as a wildcard;

asterisk (*) -used as a wildcard;

greater than (> ) -used to redirect input;

less than ( <) -used to redirect input;

While (?,*, <,> ) - are reserved character they can be used in Linux file names(it is not recommended).

File names in Linux, are case sensitive. The file names "FILE" and "file" refer to different files.

File names can be as short as a single character or can go up to 255 bytes.

File names must be unique within a directory, but many files with the same name can reside in different dir.

Filename extensions

Extensions are file name suffixes that start with a period.Linux can read many file extensions.Often, the directory where a file is placed is a better indication of what type of file it is.

Linux has no concept of a "file extension" like legacy operating systems. You may name files any way you like.The contents/purpose of a file is determined by other means.But extensions are still used to identify the content.

List of Linux file extension and the file type(content type):

Extension	File Type
.bz2	A file compressed using bzip2 .
.c	A file written in the C programming language.
.conf	A configuration file.
.lock	A lock file that prevents the use of another file.
.rpm	A Red Hat package file....ing the alien utility .
.so	A shared object (a library or module).
.src	A source code file. Wri...be compiled to be used.
.tar	A single file made of a... using the tar command.
.tar.gz	A single file made of a...ressed used the gzip command.
.tgz	A single file made of a... used the gzip command.
.gz	A file compressed using the gzip command.
.txt	a plain ASCII text file
.ps	a PostScript file; formatted for printing
.au	an audio file
.wav	an audio file
.xpm	an image file
.jpg	a graphical or image fi...h as a photo
.gif	a graphical or image file
.pdf	an electronic image of a document
.a	an archive file
.h	a C or C++ program language header file
.cpp	a C++ program language source code file
.o	a program object file
.php	a PHP Script
.sh	a Shell Script
.png	a graphical or image file
.tcl	a TCL script
.pl	a Perl script
.html/.htm	an HTML file