Section 3.12. Absolute and Relative Pathnames

[Page 52 (continued)]

3.12. Absolute and Relative Pathnames

Before I continue with the sample Linux session, it's important to introduce you to the idea of pathnames.

---

[Page 53]

Two files in the same directory may not have the same name, although it's perfectly OK for several files in different directories to have the same name. For example, Figure 3-9 shows a small hierarchy that contains a "ksh" process and three files called "myFile."

Figure 3-9. Different files may have the same name.

Although these files have the same name, they may be unambiguously specified by their pathname relative to "/," the root of the directory hierarchy. A pathname is a sequence of directory names that lead you through the hierarchy from a starting directory to a target file. A pathname relative to the root directory is often termed an absolute or full pathname. Figure 3-10 shows the absolute pathnames of the "A," "B," and "C" instances of "myFile."

Figure 3-10. Absolute pathnames.

File	Absolute PathName
A	/home/glass/myFile
B	/home/myFile
C	/bin/myFile

A process may also unambiguously specify a file by using a pathname relative to its current working directory. The Linux file system supports special fields that may be used when supplying a relative pathname (Figure 3-11).

Figure 3-11. Current and parent directories. (This item is displayed on page 54 in the print version)

Field	Meaning
.	current directory
..	parent directory

For example, Figure 3-12 shows the pathnames of the three instances of "myFile" relative to the "ksh" process located in the "/home/glass" directory.

---

[Page 54]

Figure 3-12. Relative pathnames.

File	Relative Pathname
A	myFile
B	../myFile
C	../../bin/myFile

Note that the pathname "myFile" is equivalent to "./myFile," but the second form is usually not used unless you need to specify a command in your current directory when "." is not in your search path (more on this later).