Q: What does the \n mean in those strings?
A: '\n' signifies a newline character, so the startup information doesn't appear on the same line as the first prompt.
Q: Write a program to remove trailing blanks and tabs from each line of input, and to delete entirely blank lines.
A:
#include <stdio.h>
#define MAXLINE 1000
int get_a_line(char s[], int lim);
void chop(char s[], int lim);
int main(void)
{
int len;
char line[MAXLINE];
while ((len = get_a_line(line, MAXLINE)) > 0) {
if (line[0] == '\n') {
// Nothing happens. We want to totally ignore strings that are just
// newlines.
} else {
chop(line, MAXLINE);
printf("%s<---End Of String\n", line);
}
}
return 0;
}
// Same as the previous exercise.
int get_a_line(char s[], int lim)
{
int c, i;
for (i = 0; i < lim-1 && (c=getchar()) != EOF && c != '\n'; ++i) {
s[i] = c;
}
if (c == '\n') {
s[i] = c;
++i;
}
s[i] = '\0';
return i;
}
void chop(char s[], int lim) {
int i;
// First we find the end of the string.
// Notice that the the resulting value of 'i' is the length of the string.
// Also notice that in this context, we could have just moved to the newline
// before the null char.
for (i = 0; s[i] != '\0'; ++i) {
}
// Now move backwards again, untill we find something that's not whitespace.
for (i -= 1; s[i] == '\t' || s[i] == '\n' || s[i] == ' '; --i) {
}
// And we replace whatever is after with a null char.
// We're replacing the newline, even though the exercise doesn't tell us
// to get rid of it. This is becuse it makes the output easier to test.
s[i+1] = '\0';
}
./trimmer
hi (enter)
hi<---End Of String
how are you? (enter)
how are you?<---End Of String
(enter)
three little birds(enter)
three little birds<---End Of String
Q: Write a program to print all input lines that are longer than 80 characters.
A:
/* This is really a simpler version of the longest-line program: that already
* has most of what we need. */
#include <stdio.h>
#define MAXLINE 1000
int get_a_line(char s[], int lim);
int main(void)
{
int len;
char line[MAXLINE];
while ((len = get_a_line(line, MAXLINE)) > 0) {
if (len > 80) {
printf("%s", line);
}
}
return 0;
}
int get_a_line(char s[], int lim)
{
int c, i;
for (i = 0; i < lim-1 && (c=getchar()) != EOF && c != '\n'; ++i) {
s[i] = c;
}
if (c == '\n') {
s[i] = c;
++i;
}
s[i] = '\0';
return i;
}
This is a short sentence, which will not be repeated.
This, however, is a very, very, very long sentence, which will be repeated back by the program.
This, however, is a very, very, very long sentence, which will be repeated back by the program.
Q: Add an extra message to the Version and Exit Information.
A:
...
int main(int argc, char** argv) {
puts("Lispy Version 0.0.0.0.1, Something Something Something");
puts("Press Ctrl+c to Exit. Happy Trails!\n");
while (1) {
/* Now in either case readline will be correctly defined */
char* input = readline("lispy> ");
add_history(input);
printf("No you're a %s\n", input);
free(input);
}
return 0;
}
...
Q: Revise the main routine of the longest-line program so it will correctly print the length of arbitrarily long input lines and as much as possible of the text.
A:
...
int main(void)
{
int len;
int max;
char line[MAXLINE];
char longest[MAXLINE];
max = 0;
while ((len = get_a_line(line, MAXLINE)) > 0) {
if (len > max) {
max = len;
copy(longest, line);
}
// Following tradition, we will be ignoring the null character that marks
// the end of every string. The standard library function strlen() also
// ignores null characters.
printf("Length: %d\n", len - 1);
printf("Line: %s\n", line);
}
if (max > 0) {
printf("%s", longest);
}
return 0;
}
...hi
Length: 2
Line: hi
there this is an
Length: 16
Line: there this is an
arbitrarily long string
Length: 23
Line: arbitrarily long string
moo
Length: 3
Line: moo
arbitrarily long string