1. 直接编译，会自动生成 a.out 文件，此文件即为可执行文件
# 编译 *.c 文件，生成可执行文件 a.out gcc euclide.c # 直接运行如下，如果没有输入和输出文件的话 # < input.txt # > output.txt # 可以增加参数值 ./a.out
下面代码可以生成相同用户名的 .o 文件，生成 getchar.o 文件
# -c - Compile and assemble, but do not link. gcc -c getchar.c
下面代码可以生成指定名称的 executable，生成 getchar 文件
# -o <file> - Place the output into <file>. gcc getchar.c -o getchar # 也可以 gcc -o getchar getchar.c
2. 运行时间计算，使用 time 命令
The time command returns:
- real = time you wait (not useful, systems multitask), also called clock time
- user = CPU time when your program is actually running
- sys = CPU time taken in system calls (your program is not running but is still using time)
Hence the user + sys time is the actual time taken by the program.
代码如下
alex@alex-VirtualBox:~/Documents/COMP9024/Lectures/Week01$ gcc euclid.c alex@alex-VirtualBox:~/Documents/COMP9024/Lectures/Week01$ ./a.out 1 alex@alex-VirtualBox:~/Documents/COMP9024/Lectures/Week01$ time ./a.out 1 real 0m0.002s user 0m0.001s sys 0m0.001s alex@alex-VirtualBox:~/Documents/COMP9024/Lectures/Week01$ date Mon 24 Jun 15:38:06 AEST 2019 alex@alex-VirtualBox:~/Documents/COMP9024/Lectures/Week01$ time date Mon 24 Jun 15:38:08 AEST 2019 real 0m0.001s user 0m0.000s sys 0m0.001s alex@alex-VirtualBox:~/Documents/COMP9024/Lectures/Week01$ time sleep 3 real 0m3.015s user 0m0.002s sys 0m0.000s
3. 写的话就正常写，跟 Windows 也没啥区别，虽然 gedit 显示的很舒服，但是没有语法提示。。
编译的话就通过命令实现：
# 编译使用 gcc # fgets.c 为 源代码 # -o # fgets 为可执行文件 gcc fgets.c -o fgets
程序运行如下：
# fgets 为可执行文件，注意调用的时候需要添加 ./ 的部分 # < test.txt 表示文件内容标准输入，注意此时没有 ./ 的部分 # 不造为什么哈，也懒得查啦。。 ./fgets < test.txt
Ubuntu 运行效果：
4. echo 输出内容
Reminder: the echo command just sends the string arguments to stdout (i.e. the screen here)
alex@alex-VirtualBox:~/Documents/COMP9024/Lectures/Week01$ echo love is blind love is blind
作为输入参数，echo 输出的 owl，作为 后面程序的输入参数
// prog.c
#include <stdio.h>
int main(){
char a[10];
fgets(a, 10, stdin);
printf("%s\n", a);
return 0;
}
编译效果如下，如果直接运行文件，会提示字符串输入
# 编译 gcc prog.c # 输出 owl 作为 后面可执行文件的输入参数 echo owl | ./a.out # input 里面存储的就是 owl，可以实现与上面一样的效果 ./a.out < input
5. 获取帮助
可以通过 命令名称 --help
或者 help 命令名称 来实现
gcc --help help echo
6. There are many ways to 'test' a program that reads stdin.
- scanf()
- getchar()
- Using the keyboard
直接输入相应的内容 - Using a data file
将内容写入到文件中，通过小于号实现导入文件内容 - Using a pipe command. A pipe command joins the stdout of a program to the stdin of another program.
通过竖线隔开，左边为输出，然后将其输入到右边
# Using the keyboard prompt$ dcc -o counts counts.c prompt$ ./counts 10 1 2 3 4 5 6 7 8 9 10 #where the integer 10 was typed on the keyboard by the user, and the program generates #the count from 1 to 10. #Using a data file, input.txt say, which contains the integer 10 (followed by a newline). prompt$ more input.txt 10 prompt$ ./counts < input.txt 1 2 3 4 5 6 7 8 9 10 #Using a pipe command. A pipe command joins the stdout of a program to the stdin of #another program. If we have a program called write10.c: #then we can pipe its stdout to the stdin of our counting program prompt$ dcc -o write10 write10.c prompt$ dcc -o counts counts.c prompt$ ./write10 | ./counts 1 2 3 4 5 6 7 8 9 10 #But you can actually generate a string much more easily in UNIX using echo prompt$ echo "10" | ./counts 1 2 3 4 5 6 7 8 9 10
7. shell 命令
- more：用来查看文件内容
- zip：用来压缩文件
- -r Option:【文件夹】 To zip a directory recursively, use the -r option with the zip command and it will recursively zips the files in a directory. This option helps you to zip all the files present in the specified directory.
$zip –r filename.zip directory_name - 参考：ZIP command in Linux with examples
- -r Option:【文件夹】 To zip a directory recursively, use the -r option with the zip command and it will recursively zips the files in a directory. This option helps you to zip all the files present in the specified directory.