Description
This lab will introduce you to the use of files in ANSI C, and scanning options from
the command line. Use the command man(1) to read about various commands and
functions that are mentioned in this document. For each function, the synopsis
shows you what header needs to be included, and also displays the prototypes for
relevant library functions.
1. Program Specification
The program specification is given in the format of a Unix man(1) page.
NAME
cmatch—print matching lines from files
SYNOPSIS
cmatch [-iln] string [filename …]
DESCRIPTION
cmatch searches the named input files for lines containing the string. By
default the matching lines are printed. If more than one file is specified, lines
of output are preceded by the filename.
OPTIONS
Options are scanned using getopt(3) and are subject to its restrictions and conventions.
-i Ignore case distinctions between the string and the contents of files.
-l Suppress normal output. Print only the names of files for whichamatch
is found.
-n Prefix each line of output with the line number starting from 1 within
each file.
OPERANDS
The first operand is required and is the string to be used to search the files.
The rest of the operands are filenames to be processed in sequence. If no filenames are specified, stdin is read. If a file is specified as a single minus (-)
stdin is read at that point.
EXIT STATUS
0 No errors were detected.
1 Errors were detected and messages printed to stderr, either for invalid
options or inaccessible files.
SEE ALSO
grep(1)
2. Implementation Sequence
Following are suggestions as to implementation sequence, which may be followed
CMPS-012M • Fall 2013 • Lab 4 • stdio, getopt page 2 of 2
more or less, but are not absolutely required if you find a better way.
(a) Study the behavior of pmatch.perl, which is an implementation of your lab in
Perl.
(b) Create a build script called mk as you did with the previous project. This script
uses
gcc -g -O0 -Wall -Wextra -std=gnu99
to compile cmatch.c into the executable binary cmatch. Note that an executable
binary generally does not have a suffix.
(c) Whenever you see a reference to a function in C, read the man page for it. For
example, the function strstr(3) can be discovered with the command
man -s 3 strstr
Note that in this case, the synopsis shows you what the arguments and results
to the function is, and that you need to include the header .
(d) The example catbychar.c shows how to read a file one character at a time.
(e) The example catbyline.c shows how to read a file one line at a time, assuming
the maximum line length is known.
(f) A file is opened with fopen(3) and closed with fclose(3), unless it is stdin,
which is already opened when the program begins.
(g) Error messages are printed to stderr, and fflush(3) should be called before
and after printing a message in order to ensure that the buffers are cleared.
(h) The example getoptex.c shows how to use getopt(3) to scan options given to a
program and record each as a boolean flag in a struct. Invalid options are handled.
(i) For getopt(3), the variable opterr allows us to print messages our own way,
optopt is the option character actually found, and optind is the index into argv
which is the first operand.
(j) Open a file called cmatch.c, which is mostly a copy of catbyline.c, and add the
function from getoptex.c to ensure that options are scanned.
(k) For each line read, instead of just printing it, check it against the pattern
string. Use either strstr(3) or strcasestr(3) as required by the options.
(l) Add in code to print filenames and line numbers as per the options, and make
sure the exit status is correct.
3. What to Submit
Submit the file cmatch.c as per the specifications, and the build script mk. Also submit PARTNER if you do pair programming.
