COMP1521 2020T3 Q3 · 9 marks · C 知识点: 进程/系统调用（PROC） · 次: getenv+字符串转整数 · 难度: 中等 Topic: Processes & syscalls · Source: https://cgi.cse.unsw.edu.au/~cs1521/26T1/resources/practice_exams.html
一句话 / Summary: 环境变量整数相近判断(默认42)
Write a C program, 20t3final_q3.c , which takes two names of environment variables as arguments. 20t3final_q3.c should print 1 iff both environment variables are set to a similar integer value.
20t3final_q3.c should print 0 otherwise.
Two integer values are similar if they differ by, strictly, less than 10 .
So 37 and 42 are similar .
So 52 and 42 are not similar .
An unset environment variable should be assumed to have value 42
The shell command export sets an environment variable to a value; the shell command unset unsets an environment variable.
In the following example, export is used to set the environment variables VAR1 , VAR2 and VAR3 and unset is used to ensure environment variable VAR4 is not set.
export VAR1=40 export VAR2=45 export VAR3=55 unset VAR4 dcc 20t3final_q3.c -o 20t3final_q3 ./20t3final_q3 VAR1 VAR2 1 ./20t3final_q3 VAR3 VAR2 0 ./20t3final_q3 VAR2 VAR4 1 ./20t3final_q3 VAR4 VAR3 0
There is no supplied code for this question.
Your program can assume it is always given 2 arguments.
You program can assume that if an environment variable is set it contains a valid integer and nothing else.
Your program should always print one line of output to stdout.
The line of output should contain only a single character: 0 or 1, and a newline.
Your solution must be in C only.
You are not permitted to run external programs.
You are not permitted to use system, popen, posix_spawn, fork or exec.
🤖 Adapted: read TWO lines from stdin = the two integer values (
<unset>means the variable is unset and is treated as 42). Print1iff the two values differ by strictly less than 10, else0.Verified on the sandbox AND cross-checked against an independent oracle.