Mugius lab1 submission

ANSWERS.md

@@ -19,128 +19,161 @@ Please use [markdown](https://help.github.com/articles/markdown-basics) formatin
 
 Make another directory inside the `unixstuff` directory called `backups`
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** 'cd unixstuff' 'mkdir backups'
 
 ###Exercise 1b
 
 Use the commands `cd`, `ls` and `pwd` to explore the file system.
 
 (Remember, if you get lost, type `cd` by itself to return to your home-directory)
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** 'pwd' 'ls -a' 'cd Documents/opsys/labs/lab1' 'cd'
 
 ###Exercise 2a
 
 Create a backup of your `science.txt` file by copying it to a file called `science.bak`
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** 'cp science.txt science.bak'
 
 ###Exercise 2b
 
 Create a directory called `tempstuff` using `mkdir`, then remove it using the `rmdir` command.
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** 'mkdir tempstuff' 'rmdir tempstuff'
 
 ###Exercise 3a
 
 Using the above method, create another file called `list2` containing the following fruit: orange, plum, mango, grapefruit. Read the contents of `list2`.
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** 'cat > list2'
+'orange
+plum
+mango
+grapefruit'
+'cat list2'
 
 ###Exercise 3b
 
 Using pipes, display all lines of `list1` and `list2` containing the letter 'p', and sort the result.
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** 'cat list1 list2 | grep p | sort'
 
 ###Exercise 5a
 
 Try changing access permissions on the file `science.txt` and on the directory `backups`.
 
 Use `ls -l` to check that the permissions have changed.
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** 'chmod 777 science.txt' 'chmod 777 backups'
 
 ##Shell questions
 
 1. What option with the command `rm` is required to remove a directory?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'rm -r dirname'
 1. What is the command used to display the manual pages for any command?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'man command'
 1. What command will show the first 5 lines of an input file?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'head -5 filename.txt'
 1. What command can be used to rename a file?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'mv oldfilename.txt newfilename.txt'
 1. What option can we given to `ls` to show the hidden files?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'ls -a'
 1. What will the command `cat -n file` do?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** Gives a number to all output lines in the file
 1. What will the command `echo -n hello` do?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** Outputs hello, but with no newline after it
 1. What command will display s list of the users who currently logged in in the system?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'who'
 1. How do you change password on your account?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'sudo passwd USER'
 1. How can you list a file in reverse order?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'tac FILENAME'
 1. What does the `less` command do?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** display a file with one page at a time
 1. With `less` how do you navigate?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** spacebar - next page
 1. What command will display the running processes of the current user?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'ps'
 1. What command can be used to find the process(es) consuming the most CPU?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'ps -aux | head -2' 
 
 ##vi questions
 1. How do we save a file in `vi` and continue working?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** ":w"
 1. What command/key is used to start entering text?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'i'
 1. What are the different modes the editor can be in?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** Insert, commando'
 1. What command can be used to place the cursor at the beginning of line 4?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** ':4' 
 1. What will `dd` command do (in command-mode)?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** Deletes the line that the cursor is in
 1. How do you undo the most recent changes?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'u' in commando-mode
 1. How do you move back one word?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'b' in commando-mode
 
 ##The C Language and Make tool Questions
 
 1. How do you use `gcc` to only produce the `.o` file?  What is the difference between generating only the `.o` file, and building the `hello` executable done in the previous compilation above?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'gcc -c filename.c -o filename.o' The file can be used to build an exe file later by combining several object files together. The debug info is stored in the object file. 
 1. Give the command for compiling with `debug` enabled instead of normal compilation for the two examples shown in Listing 2 and Listing 3. Explain how to turn debugging on/off for the two cases.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** gcc -g filename.c -o filename' 
 1. Give a brief pros and cons discussion for the two methods to add debug code shown in Listing 2 and Listing 3.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** Listing 2 only includes debug if it is defined when compiling the program, Listing 3 always includes debug, thus having unnecassery code(bigger exe file). 
 1. Provide the command for generating the *map* file. Which of the `gcc` tools is responsible for producing a *map* file?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'gcc -Wl,-Map=main.map test.c' Linker is responsible for producing a map file. 
 1. What is the content of each of the sections in a *map* file. Explain briefly.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** Discarded input sections, Memory configuration, Linker script and memory map. .text has machine instructions that defines the program. Under .text we have .initN that is used as startup code up till main() and .finiN that is used to define the code that is used after main(). .bss includes non-initialized rw global or static variables or values that are initialized as null. .data has rw static data that are created in the code. .rodata has constant read-only data.  
 1. Rewrite `hello.c` to produce entries in the *map* file for `.data`, `.bss`, and `.rodata`. Hint: This can be done by adding one variable for each type to the file.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'int datavariable = 11;
+int bss;
+static const float rodatavariable = 13.37f;
 1. Add the following function to `hello.c`: `double multiply(double x1, double x2)`, which returns `x1*x2`. Use `gcc` to generate an assembly code listing for the program, and examine the assembly code. What assembly instructions are used to do this? Repeat this task, but now replace `double` with `float`. Explain!
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** Double has more bits. When it is double, assembly code uses: 'movsd/mulsd', while when it is float, 'movss/mulss' is used. 
 1. How does `make` know if a file must be recompiled?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** It recompiles a file because its conservative and assumes that any change in the header file requires recompilation of all dependent files. Newer timestamps will also make it recompile. 
 1. Provide a `make` command to use a file named `mymakefile` instead of the default `makefile`.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** 'make -f mymakefile'
 1. How do you implement an *include guard*, and why is it needed?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** '#ifndef RANDOM_M
+#define RANDOM_M
+.
+.
+.
+#endif' It is needed because it guards from compilation error when the structure type is defined twice. 
 
 ##Library Task
 
 Insert your code between the brackets `{}`:
 
     void main( int argc, char *argv[] )
 	{
+	int antall;
+	sscanf(argv[1], "%d", &antall);
+	double table[antall];
+	int i;
+	for (i = 0; i < antall; i++)
+	{
+		table[i] = rand() % 100 + 1;
+		printf("%.2f\n", table[i]);
+	}
+	double sum = tab_sort_sum(table, antall);
+	printf("Sum is %1f\n" sum);
     }
 
 	double tab_sort_sum( double *tab, int tab_size )
 	{
+		qsort(table, table_size, sizeof(double), comp);
+		double sum;
+		int i;
+		printf("sorted:\n");
+		for (i = 0; i < tab_size; i++)
+		{	
+			printf("%.2f\n", tab[i]);
+			sum += tab[i];
+		}
+		return sum;
 	}
 
 

Makefile

@@ -0,0 +1,2 @@
+main: main.c l1.h
+	gcc main.c -o main

hello.c

@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+int main(void)
+{
+	printf("Hello, world!\n");
+	return 0;
+}
+
+
+float multiply(float x1, float x2)
+{
+	return x1*x2;
+}

hello.s

@@ -0,0 +1,46 @@
+	.file	"hello.c"
+	.section	.rodata
+.LC0:
+	.string	"Hello, world!"
+	.text
+.globl main
+	.type	main, @function
+main:
+.LFB0:
+	.cfi_startproc
+	pushq	%rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset 6, -16
+	movq	%rsp, %rbp
+	.cfi_def_cfa_register 6
+	movl	$.LC0, %edi
+	call	puts
+	movl	$0, %eax
+	leave
+	.cfi_def_cfa 7, 8
+	ret
+	.cfi_endproc
+.LFE0:
+	.size	main, .-main
+.globl multiply
+	.type	multiply, @function
+multiply:
+.LFB1:
+	.cfi_startproc
+	pushq	%rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset 6, -16
+	movq	%rsp, %rbp
+	.cfi_def_cfa_register 6
+	movss	%xmm0, -4(%rbp)
+	movss	%xmm1, -8(%rbp)
+	movss	-4(%rbp), %xmm0
+	mulss	-8(%rbp), %xmm0
+	leave
+	.cfi_def_cfa 7, 8
+	ret
+	.cfi_endproc
+.LFE1:
+	.size	multiply, .-multiply
+	.ident	"GCC: (GNU) 4.4.7 20120313 (Red Hat 4.4.7-4)"
+	.section	.note.GNU-stack,"",@progbits

l1.h

@@ -0,0 +1,20 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+int comp(const void * a, const void * b) {
+	return ( *(double*)a - *(double*)b );
+}
+
+double tab_sort_sum( double *tab, int tab_size )
+{
+	qsort(tab, tab_size, sizeof(double), comp);
+	double sum;
+	int i;
+	printf("sorted:\n");
+	for (i = 0; i < tab_size; i++)
+       	{
+		printf("%.2f\n", tab[i]);
+		sum += tab[i];
+	}
+	return sum;
+}

main.c

@@ -0,0 +1,21 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include "l1.h"
+double tab_sort_sum(double *, int);
+
+
+void main( int argc, char *argv[] )
+{
+	int antall;
+	sscanf(argv[1], "%d", &antall);
+	double table[antall];
+	int i;
+	for (i = 0; i < antall; i++) 
+	{
+		table[i] = rand() % 100 + 1;
+		printf("%.2f\n", table[i]);
+	}
+	double sum = tab_sort_sum(table, antall);
+	printf("Sum is %1f\n", sum);
+}
+