Lab $11$: Strings, ENV and File I$/$O System Calls

Overview:

We will read from a CSV file identified on the command line $($e$.$g$.$ include$/$data$.$csv$).$ The data file which contains lines of comma separated data elements. For each csv line, write the processed data in the format specified below to the terminal screen $($stdout$).$

We will be using the open$(),$ read$()$ and close$()$ system calls as well as some of the standard C library string functions. Our output file name will be specified in the environment.

New String Function:

Send all error messages to standard error $($stderr$).$ Use the string function snprintf$()$ to formaterror messages sent to perror$().$ Look at snprintf man page, and$/$or HERE for more info on using this string function.

You can also use snprintf$()$ for assembling the output line for each csv data line.

Here's an example of snprintf$()$ usage:

char msg$[80]$;

snprintf$($msg$,$ sizeof$($msg$),$ "Error opening file: $",$ inFile$)$;

perror$($msg$)$ ;

Steps:

$-$ Create your project directory "lab$11"$ in the usual location alongside your other labs

$-$ Your project directory, you'll create the following structure:

$-$ sre $\backslash (\backslash$quad $\backslash$leftarrow $\backslash )$ contains lab$11.$c and utils.c

$-$ include $\backslash (\backslash$leftarrow $\backslash )$ contains lab$11.$h

$-$ data $\backslash (\backslash$leftarrow $\backslash )$ contains data.dat file, download from Canvas

$-$ Create a makefile under the src directory, which you will adjust as you go$.$

$-$ Create a lab$11.$c which holds your main$(),$ processes command line arguments, determines the file name $($see below$),$ opens the input data file and calls other functions to perform the work.

$-$ Create a utils.c in your src directory which contains functions for processing the data.

$-$ Create a lab$11.$h in the include directory which holds any needed typedefs, $\backslash$#defines, extern declarations, etc

$-$ Open the input data file identified in the INFILENM environment variable using the system call open$()-$ Read only

$-$ Print to stdout the following line to display the length of the file name:

File name $""$ is chars long

$-$ Where is the name of the data file, and is the length of the file name, using strlen$().$ Include the quotes around the file name in your display. $-$ Loop through reading lines of the input data file $($a $"$csv$"$ line$)$

$-$ Use strtok$()$ to parse the separate elements from the csv line.

$-$ You will reformat the $4$ comma separated data elements on each line of the data file into a single output line $($see below$)$ Hint: another use for snprintf$()$

$-$ Note: strtok$()$ doesn't have to be called in a loop, you can just call it $4$ times.

$-$ For each parsed line, use the following functions from string.h:

$-$ strcpy$()\backslash$& strcat$()-$ to combine the first and last name from the data file together to be in a single variable in the form $",".$

$-$ strcmp$()$ to determine the sort order of and based on the ASCII values of the characters in the two strings. $($display or $">"$ based on the comparison. e$.$g$.$ "Adam" is less than "Bill" so display $"[<mi>]</mi><mi>"</mi>$

$-$ strstr$()$ to check if their favorite quote contains the substring "cat"

Print the following line for each of the csv lines read:

Data line: ID$=$ Name: $[]$

Where is the or $>$ display and is the string "Does have a cat" or "Does NOT have a cat" depending on the results of strstr$()$

For example: Read the csv line $"4372,$Bill,Johnson,I am a doctor not a cat"

Data Line: ID$=4372$ Full Name $=$ Johnson, Bill $[<mi>]</mi>$ Does have cat

Data:

The data file is a Comma Separated Value $($CSV$)$ file with fixed width lines of $50$ characters. This file is provided in the Canvas Assignment. You'll read into a buffer of size $\backslash (50+1\backslash )$ to account for the new line character at the end of each csv data line.

$-$ The individual data elements in the line are all strings, in order from left to right in the file they are:

$-$ Here is what the content of that file looks like:

$,,,$

$-$ The actual data, but need to have the right length of data lines since we're using read$()$ to read in a data line of a particular length.

$```$

$4372,$Bill,Johnson, I am a doctor not a cat

$4395,$ Betty,Smith, I have a dream

$4672,$Hank,Blusefield, I have a cat

$4337,$ Phillip,Phillip, Where's my cat!?!

$4330,$ Zelda,Nozzel,Ask not what you can do

$```$ Output:

The output from the program should look as follows $($just showing output for one input data line, your output should include all input data lines:

Data Line: ID$=4372$ Full Name $=$ Johnson, Bill $[<mi>]</mi>$ Does have cat

Note: the read$()$ system call will include newlines, and not include a NULL to terminate the csv line we would like to treat as a string. So$,$ use something like this for reading lines from the csv data file with the read$()$ system call into a string value without the newline:

LINELEN is defined as $51$ for reading lines of length $50$ to account for the $\text{'}\backslash (\backslash$ n $\backslash )\text{'}$

$```$

$/*$ Load the data in from the $.$csv file $*/$

void loadList$($int inFileFD$)\{$

int numRead;

char $*$ buf $=$ calloc$($LINELEN$,$ sizeof$($char$))$;

while $(($numRead $=$ read$($inFileFD$,$ buf, LINELEN$))>0)\{$

buf$[$LINELEN$-1]=\text{'}\backslash 0\text{'}$; $//$ replace the

with a NULL

printf$("$Read line: $=\%$s$=$

$",$ buf$)$;