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Programming with Pointers in C Assignment Help

The assignment is separated into 4 different problems. The first problem deals with using command line arguments in C. The memory addresses used to pass the arguments are printed on the screen in hexadecimal form. Both the variable names and addresses are shown as output following a format similar to the gdb output. The second program deals with handling complex command-line arguments following a predefined format that consists of options with parameters and optional filenames. Problem 3 deals with environment variables in C, it allows to read and sort the environment variables present when the program is executed. The last problem deals with sorting an array of integers provided from the standard input and saved in a linked list. The program uses bubble sort to make the sorting and uses structures to build the required linked list. The following code provided by our C programming assignment helpers shows you how to use pointers in C.

Processing and Printing Command Line Arguments in Hexadecimal

Programming with Pointers in C Assignment Help

#include #include int main(int argc, char **argv, char **envp) { int i, j; char *temp; /* sort environment variables using bubble sort */ for (i = 0; envp[i] != NULL; i++) /* repeat until a NULL is found */ { strtok(envp[i], "="); /* separate variable name from value */ for (j = i + 1; envp[j] != NULL; j++) /* compare remaining variables */ { strtok(envp[j], "="); /* separate variable name from value */ /* if not in order */ if (strcmp(envp[i], envp[j]) > 0) { /* swap */ temp = envp[i]; envp[i] = envp[j]; envp[j] = temp; } } } /* print all variables */ for (i = 0; envp[i] != NULL; i++) { envp[i][strlen(envp[i])] = '='; /* add missing = removed by strtok */ printf("%s\n", envp[i]); } return 0; } #include #include #include /* Prints the given pointer contents as a series of 8 bytes */ void print_hex_pointer(void *value) { int i; char *c; c = (char *) value; for (i = 7; i >= 0; i--) /* print from msb to lsb */ { if (i < 7) printf(" "); printf("%02hhx", c[i]); } } int main(int argc, char **argv) { int i; char c; char *pointer; char *last; /* print argv contents and pointer */ printf("argv | "); print_hex_pointer(&argv); printf(" | %p\n", &argv); printf("\n"); /* print all argv argument pointers */ for (i = 0; i < argc; i++) { printf("argv[%d] | ", i); print_hex_pointer(&argv[i]); printf(" | %p\n", &argv[i]); } printf("\n"); /* print memory contents */ pointer = argv[0]; /* start of memory to be printed */ pointer = (char *)((long)pointer & -8); /* align to 8 bytes */ last = argv[argc - 1] + strlen(argv[argc - 1]); /* address of last char */ while (pointer <= last) { printf(" | "); for (i = 7; i >= 0; i--) /* print from msb to lsb */ { c = pointer[i]; if (isprint(c)) /* if printable */ printf("%02hhx(%c) ", c, c); else /*non printable, use escape */ printf("%02hhx(\\%hhu)", c, c); printf(" "); } printf("| %p\n", pointer); pointer += 8; /* advance pointer 8 bytes */ } printf("\n"); return 0; } #include #include struct node { int value; struct node *next; }; int main(int argc, char **argv, char **envp) { int number; struct node *head, *tail, *new_node, *temp; struct node *inode, *jnode, *iprev, *jprev; head = NULL; /* initially list is empty */ tail = NULL; /* tail is null */ while(scanf("%d", &number) != EOF) { new_node = (struct node *) malloc(sizeof(struct node)); if (new_node == NULL) { printf("Out of memory!\n"); return 1; } new_node->value = number; /* save read number */ new_node->next = NULL; if (head == NULL) /* if new list, use node as list */ { head = new_node; tail = head; /* tail is first node */ } else /* else, attach at tail */ { tail->next = new_node; tail = new_node; /* new node is the new tail */ } } /* sort nodes using bubble sort */ for (inode = head, iprev = NULL; inode != NULL; iprev = inode, inode = inode->next) /* repeat until a NULL is found */ { for (jnode = inode->next, jprev = inode; jnode != NULL; jprev = jnode, jnode = jnode->next) /* compare remaining variables */ { /* if not in order */ if (inode->value > jnode->value) { /* swap links */ if (jprev != inode) /* if not near */ { temp = jnode->next; jnode->next = inode->next; if (iprev != NULL) iprev->next = jnode; inode->next = temp; jprev->next = inode; } else { if (iprev != NULL) iprev->next = jnode; inode->next = jnode->next; jnode->next = inode; } /* fix head and tail pointers */ if (inode == head) head = jnode; if (jnode == tail) tail = inode; /* swap i and j pointers */ temp = inode; inode = jnode; jnode = temp; } } } /* print all numbers */ for (inode = head; inode != NULL; inode = inode->next) { printf("%d\n", inode->value); } /* free all list */ inode = head; while (inode != NULL) { temp = inode; inode = inode->next; free(temp); } return 0; } #include #include int main(int argc, char **argv) { int opt; int copt, dopt, uopt, fopt, sopt; char *ffields, *schar, *infile, *outfile; copt = 0; /* no -c */ dopt = 0; /* no -d */ uopt = 0; /* no -u */ fopt = 0; /* no -f */ sopt = 0; /* no -s */ ffields = NULL; ffields = NULL; schar = NULL; infile = NULL; outfile = NULL; opterr = 0; /* don't print errors from getopt */ /* read all options using the command line parameters: my_uniq [-c|-d|-u] [-f fields] [-s char] [input_file [output_file]] */ while ((opt = getopt(argc, argv, ":cduf:s:")) != -1) { switch(opt) { case 'c': copt = 1; break; case 'd': dopt = 1; break; case 'u': uopt = 1; break; case 'f': fopt = 1; ffields = optarg; break; case 's': sopt = 1; schar = optarg; break; case ':': if (optopt == 'f') printf("Option -f requires an argument\n"); else if (optopt == 's') printf("Option -s requires an argument\n"); return 1; case '?': /* ? */ printf("Invalid option -%c\n", optopt); return 1; default: printf("Invalid option %c\n", opt); return 1; } } /* print the options given: */ printf("-c = %d\n", copt); printf("-d = %d\n", dopt); printf("-u = %d\n", uopt); printf("-f = %d, fields = %s\n", fopt, ffields); printf("-s = %d, char = %s\n", sopt, schar); if (optind < argc) /* if there an input file was given */ infile = argv[optind]; if (optind + 1 < argc) /* if there an output file was given */ outfile = argv[optind + 1]; printf("input_filename = %s\n", infile); printf("output_filename = %s\n", outfile); return 0; }