02 specific implementation of LS command

Preface

// ha-ha Yesterday's was a little perfunctory , I can't say it's not a detail ? 

ha-ha This command Should be linux Users Basically, I will use it ?

ha-ha Here we are mainly to glance at How does this command work

main Mainly parameter processing , Cycle through the paths Output the information of each path

print_dir It is mainly to traverse each under the current path Sub file ( clip ), The specific business is entrusted to gobble_file, Collect each Sub file ( clip ) Information about

gobble_file Mainly used lstat/stat Command to get each file ( clip ) Related metadata of

print_current_files Mainly output each Sub file ( clip ) Information about , Here, this involves the specific output format , We are here to ls -l For example

print_long_format The output of is common ll Processing of output , Output fmode, nlink, user, group, size, mtime, fileName

be based on linux-4.4.0 + coreutils-8.25

Debugging is command based "ls -l /"

main

What you can see is ls There is only one path behind "/" 

Here is the call print_dir To output "/" Each of the following Sub file ( clip ) Information about  

print_dir 

be based on opendir, readdir And so on api Traverse "/" Each of the following Sub file ( clip ) 

call gobble_file To get each Sub file ( clip ) Related metadata of  

gobble_file 

adopt stat/lstat relevant api To get the current file ( clip ) Metadata information of  

print_current_files 

according to Output format Make different outputs , Here we are print_long_format 

print_long_format

  The function content is long , It's not finished here  

Use buf towards stdout Output  fmode, nlink 

user, group Additional system calls are required to obtain uid, gid The corresponding name , Use it directly stdout Output  

Use buf towards stdout Output  size, mtime, fileName

 

ha-ha These built-in commands Is it not so mysterious ? 

Of course Here is only the core context of analysis , Real implementation details There are also many designs  

End