A few weeks ago at the recommendation of people I trust, I bought and started reading Kernighan and Ritchie's (K&R) C Programming Language. For one thing, it's damn thin compared to the O'Reilly Practical C I just finished last month. It covers generally the same stuff but in a much more efficient manner. Of course, what do I know? I'm only on chapter 1 and I'm taking K&R's advice and pausing my reading to work through the programming problems in the chapter. One thing that's kind of frustrating to me is that I ran into a problem that seems like it could have an elegant solution, but I've not come up with one. Problem 1-9 which says:
"Write a program to copy its input to its output, replacing each string of one or more blanks by a single blank".
At first I tried coming up with my own code from scratch and wound up with some freakish binary that spit out unprintable characters (probably a mix up in data types). So I started over and entered their file copying program example (1.5.1) from page 16. Then I thought about how to modify it. Here is what I came up with:
(NOTE: I used 32 for space in the first if conditional while testing and didn't switch it back to c == ' '.)
The compiled program works on the most basic level, but I'm sure it's bug ridden and the wrong input will make it barf. Since it does what it's supposed to, I've moved on. But I'm strangely bothered since I *KNOW* there has to be a better way than a bunch of serial if conditionals. I get this nagging feeling that I could do it shorter and with fewer checks.
But I just couldn't do it. Anyone else see where I'm totally off? This is definitely beginner style code and I admit as much. But I was pretty bad in the beginning with Bash too (I had a full page script in 2001 to generate MP3 playlists by traversing directories. Today I have a two liner using the 'find' command), so I think there is hope for my dream of one day being fluent at C. Anyone have any suggestions about my above code? Where could my thinking be improved?
I'll also say that I have a lot of trouble thinking in parallel, but it seems that that is how the best coders think. My code has always been serial in DOS BAT files, CMD, Bash, Perl and now C. Any tips on changing that way of seeing things? Also, let me know if this isn't the right place to post this.
NOTE: I know there's an "answer book" for this book. But I want to do it the "hard way" first and then when I'm done I'll compare my answers with the ones in the answer book.
I have been a student at Hendrix Institute for about a year now. My term is comming to an end by the end of december. I have learned varios computer programs for web development that include Flash 5 and Dreamweaver. Actionscripting, Javascript and Database development with Access was all... (4 Replies)
All,
Have an AMD-K6/2 PC, 20G.Hd along with RH7.2.
Wanting to know what I should do in terms of setup (workstation/server) and then what I can do with it?
I'd like to learn a DBMS and SQL - can I do this using RedHat?
Any suggestions with how I can use/ what I can do with this appreciated. (3 Replies)
The current backup procedure we using a tar command in linux.
The files are stored in one partition in different folders. The docs stores in day wise folders like ex: /usr/data/xyz/20050129, /usr/data/xyz/20050130 .............etc
We using tar & gzip command to take backup everyday. The backup... (3 Replies)
We run WebSphere and by default it wants to install everything under /usr. While I can understand the default (everyone has a /usr) I would like to move this over to a dedicated volume group called apps and then setup my lv's and fs's here. Our WebSphere Admin doesn't like this because apparently... (1 Reply)
Hi all,
I have worked on HP UNIX and now i have moved to SunSolaris which i never used to work.
I am more on programming side like shell and perl scripting.
So i want to know from you experts that i need to take care or changes which i code in sun solaris in compared to HP unix.
Suggestions... (1 Reply)
Hi,
I have written a script which calls a process which ends up in a reboot of the system. At the end of the reboot it prompts for login & i need to provide the login details. am not able to figure out hw to do this.
Doubt: will echoing login details after calling the process work?
for ex:... (1 Reply)
Hello there....i am a final year comp science student.......i am thinking of doing my project on unix platform......which one do u suggest?thanx in advance... (3 Replies)
I've been busy and fell behind on Sun/Oracle. Forgive me if too basic. I welcome brief, cryptic, or advanced replies. I also welcome noobie information since I may have no clue what's up at the moment.
Problem statement:
I inherited a computer to set up. I would rather not figure out 8 months... (1 Reply)
Hi guys, i'm undergoing a traning in solaris administration and i request if any one have an idea on the interview questions on solaris.
thank you. (3 Replies)
i=1
out=""
j=`expr 2 * $1`
while
do
out="$out"#""
echo $out
((i=i+1))
done
while
do
print ${out%?}
((i=i+1))
done
This script is throwing an error:
gurnish:/home/fnb/gurnish/saurabh/scripts> while1 3
expr: 0402-050 Syntax error.
# (6 Replies)
Discussion started by: targetshell
6 Replies
LEARN ABOUT NETBSD
c99
C(7) BSD Miscellaneous Information Manual C(7)NAME
c, c78, c89, c90, c99 -- The C programming language
DESCRIPTION
C is a general purpose programming language, which has a strong connection with the UNIX operating system and its derivatives, since the vast
majority of those systems were written in the C language. The C language contains some basic ideas from the BCPL language through the B lan-
guage written by Ken Thompson in 1970 for the DEC PDP-7 machines. The development of the UNIX operating system was started on a PDP-7
machine in assembly language, but this choice made it very difficult to port the existing code to other systems.
In 1972 Dennis M. Ritchie worked out the C programming language for further development of the UNIX operating system. The idea was to imple-
ment only the C compiler for different platforms, and implement most parts of the operating system in the new programming language to sim-
plify the portability between different architectures. It follows that C is very well adapted for (but not limited to) writing operating
systems and low-level applications.
The C language did not have a specification or standardized version for a long time. It went through a lot of changes and improvements for
ages. In 1978, Brian W. Kernighan and Dennis M. Ritchie published the first book about C under the title ``The C Programming Language''. We
can think of this book as the first specification of the language. This version is often referred to as ``K&R C'' after the names of the
authors. Sometimes it is referred to as C78, as well, after the publishing year of the first edition of the book.
It is important to notice that the instruction set of the language is limited to the most fundamental elements for simplicity. Handling of
the standard I/O and similar common functions are implemented in the libraries shipped with the compiler. As these functions are also widely
used, it was demanded to include into the description what requisites the library should conform to, not just strictly the language itself.
Accordingly, the aforementioned standards cover the library elements, as well. The elements of this standard library are still not enough
for more complicated tasks. In this case the provided system calls of the given operating system can be used. To not lose the portability
by using these system calls, the POSIX (Portable Operating System Interface (for Unix)) standard evolved. It describes what functions should
be available to keep portability. Note, that POSIX is not a C standard, but an operating system standard and thus is beyond the scope of
this manual. The standards discussed below are all C standards and only cover the C programming language and the accompanying library.
After the publication of the book mentioned before, the American National Standards Institute (ANSI) started to work on standardizing the
language, and in 1989 they announced ANSI X3.159-1989. It is usually referred to as ANSI C or C89. The main difference in this standard
were the function prototypes, which was a new way of declaring functions. With the old-style function declarations, the compiler was unable
to check the sanity of the actual parameters of a function call. The old syntax was highly error-prone because incompatible parameters were
hard to detect in the program code and the problem only showed up at run-time.
In 1990, the International Organization for Standardization (ISO) adopted the ANSI standard as ISO/IEC 9899:1990. This is also referred to
as ISO C or C90. It only contains negligible minor modifications against ANSI C, so the two standards are often considered to be fully
equivalent. This was a very important milestone in the history of the C language, but the development of the language did not stop.
The ISO C standard was later extended with an amendment as ISO/IEC 9899 AM1 in 1995. This contained, for example, the wide-character support
in wchar.h and wctype.h. Two corrigenda were also published: Technical Corrigendum 1 as ISO/IEC 9899 TCOR1 in 1995 and Technical Corrigendum
2 as ISO/IEC 9899 TCOR2 in 1996. The continuous development and growth made it necessary to work out a new standard, which contains the new
features and fixes the known defects and deficiencies of the language. As a result, ISO/IEC 9899:1999 was born in 1999. Similarly to the
other standards, this is referred to after the publication year as C99. The improvements include the following:
o Inline functions.
o Support for variable length arrays.
o New high-precision integer type named long long int, and other integer types described in stdint(3) and inttypes(3).
o New boolean data type; see stdbool(3).
o One line comments taken from the C++ language.
o Some new preprocessor features.
o A predefined identifier __func__ and a restrict type qualifier.
o New variables can be declared anywhere, not just in the beginning of the program or program blocks.
o No implicit int type.
Since then no new standards have been published, but the C language is still evolving. New and useful features have been showing up in the
most famous C compiler: GNU C (gcc(1)). Most of the UNIX-like operating systems use GNU C as a system compiler, but the various extensions
of GNU C, such as attribute(3) or typeof(3), should not be considered standard features.
SEE ALSO c89(1), c99(1), cc(1), cdefs(3)
Brian W. Kernighan and Dennis M. Ritchie, The C Programming Language, Prentice Hall, Second Edition, 40th printing, 1988.
STANDARDS
ANSI, X3.159-1989.
ISO/IEC, 9899:1990, Programming languages -- C.
ISO/IEC, 9899 AM1.
ISO/IEC, 9899 TCOR1, Programming languages -- C, Technical Corrigendum 1.
ISO/IEC, 9899 TCOR2, Programming languages -- C, Technical Corrigendum 2.
ISO/IEC, 9899:1999, Programming languages -- C.
ISO/IEC, 9899:1999 TCOR1, Programming languages -- C, Technical Corrigendum 1.
ISO/IEC, 9899:1999 TCOR2, Programming languages -- C, Technical Corrigendum 2.
ISO/IEC, 9899:1999 TCOR3, Programming languages -- C, Technical Corrigendum 3.
HISTORY
This manual page first appeared in FreeBSD 9.0 and NetBSD 6.0.
AUTHORS
This manual page was written by Gabor Kovesdan <gabor@FreeBSD.org>.
BSD March 30, 2011 BSD