Viewing file content
So far, we've only looked at the covers, without opening the book. Let's give you an overview of ways of getting to know what's in a file.
The file command
Gives the type of data based on code at the beginning of the file. Note that file is not perfect, it only tries an educated guess. In the example below, for instance, file makes no difference between verlanglijst and tkConfig.sh, although the first is just ordinary text, while the second is a shell script.
tille:~>file mail mail: directory tille:~>file verlanglijst verlanglijst: ASCII text tille@sprawl:~>file nbroc2001.pdf nbroc2001.pdf: PDF document, version 1.2 tille@sprawl:~>file training/unix-basics/abook.ps training/unix-basics/abook.ps: PostScript document text conforming at level 2.0 tille@sprawl:~>file Verlofkaart2001MGA.xls Verlofkaart2001MGA.xls: Microsoft Office Document tille@sprawl:~>file images/me+tux.jpg images/me+tux.jpg: JPEG image data, JFIF standard tille@sprawl:~>file training/unix-basics/book1.html training/unix-basics/book1.html: HTML document text tille@sprawl:~>file richtlijnen.doc richtlijnen.doc: Microsoft Office Document tille:~>cd /bin tille:/bin>file gzip gzip: ELF 32-bit LSB executable, Intel 80386, version 1, ... tille:/bin>cd /usr/lib tille:/usr/lib>file libgtop.so.1.0.9 libgtop.so.1.0.9: ELF 32-bit LSB shared object, Intel 80386, ... tille:/usr/lib>file tkConfig.sh tkConfig.sh: ASCII English text tille:/usr/lib>cd /boot/ tille:/boot>file kernel.h kernel.h: symbolic link to kernel.h-2.4.2 tille:/boot>file vmlinuz-2.4.2-2 vmlinuz-2.4.2-2: x86 boot sector tille:/boot>cd /etc tille:/etc>file profile profile: ASCII text |
The cat command
Concatenates files (puts them together) and puts them to the output, with only one argument given cat will display the contents of the file
tille:~>cat test1 some words tille:~>cat test2 some other words tille:~>cat test1 test2 some words some other words |
The more, less and pg commands
While cat puts all output all at once to the screen, more filename allows to view the output page by page. Navigate through the output using the spacebar and the b-key (back).
Some systems offer the GNU less command, which has more extended features than more. "Less is more", you will hear somebody say sooner or later. less allows vi-like browsing and searching in the text. See Chapter 4: Editors for more information about the vi editor.
On some really old systems, you will find neither more nor less. The system might provide the pg utility, which provides similar functionality. Navigate to the next page pressing the enter-key.
 | Quitting the output of more, less and pg without going all through the file is done pressing "q". |
Viewing file content in X Windows
If in a graphical user environment, there are all sorts of editors and viewers that come with the system. Consult your system documentation and find your favorite.