Heads.doc Documentation for head, tail, and ends
3 AREXX programs for viewing the first/last/both ends of a file.
Herbert Wollman, Telephone (617) 272-2994
5 Fowler Ter, Burlington, MA 01803, USA.
E-mail at hwollman mitre.org
Head and tail are handy utilities for viewing the first and last lines
respectively of files. They are a standard part of any UNIX computer, and
have been ported to many other computer systems. Their default behavior is
to copy the first (or last, respectively) 10 lines from Standard Input to
Standard Output. However, like most UNIX commands, command line options
can make them much more versatile. The usage is,
head [ -LineCount ] [ File ] [ OtherFiles... ]
tail [ -LineCount ] [ File ] [ OtherFiles... ]
ends [ -LineCount ] [ File ] [ OtherFiles... ]
If the first command line parameter is a negative integer, it will specify
the number of lines copied. If the LineCount parameter is missing, it will
default to 10. Any other parameters are the names of files to read instead
of Standard Input. If more than one file is specified, the filename will
appear before each new set of lines listed.
Head and tail are standard utilities, usually written in C, available on all
UNIX computers. My Amiga versions, head.rexx, and tail.rexx included in
this archive are written in AREXX. Head.rexx is functionally identical to
the version I use at work on Silicon Graphics workstations. The UNIX
version of tail allows only one file to be specified, but my Amiga version
allows multiple files, just as head does.
Occasionally you want to view both the beginning and end of a file. For
this I have written the program ends.rexx, which has no direct UNIX
equivalent. The syntax for ends is the same as for head or tail. It will
show the first and last lines of each file, separated by a line of ...
On a UNIX computer the shell expands wildcards in the filenames on the
command line prior to passing it to a program. Hence the head program
would receive one command parameter for each file that it has to read.
However, on the Amiga, neither the standard AmigaShell, nor the WShell
(which I use), perform wildcard expansion. Therefore each program must do
its own filename expansion. To do this, I use the FileList() function in
the rexxarplib.library, which must be located in the LIBS: directory.
I have included two smaller and faster versions of head, which only perform
the default operation, and hence do not accept command line options.
Defhead.rexx (Defaulthead) is a 2 line, 158 byte program in AREXX. In
contrast, the full version of head.rexx, which can handle any number of
filename patterns on the command line, each of which can expand into many
names, is relatively large, i.e., 1290 bytes, and 59 lines.
Fhead.f is the one line source code for Fhead (Falsehead), which is written
in "False." The compiled executable is only 312 bytes. False is a
wonderful "toy" language written by Wouter van Oortmerssen, and available
on Fish Disk 885. It is perfect for this type of application, at least if
you like compact obscure code.
All of the program files in this archive are released into the public
domain, however I request that if you redistribute them, please keep them
together with this doc file. If you wish to contact me, I can be reached
via the Boston Computer Society, Amiga Bulletin Board (617) 729-7340, or by
E-mail at hwollmanmitre.org
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