Ls
Internal
Overview
List files in a directory.
Options
-d
Lists directories themselves, not their contents.
-i
List the inode number.
ls and File Time Information
Intro
Under POSIX, each file has three distinct associated timestamps:
- the time of last data access (access time, atime) - this is the time the file was last read. Can be read with ls -lu.
- the time of last data modification (data modification time, mtime) - this is the time when the file data was modified.
- the time the file status last changed ('status change time', ctime) - this is the time when the inode associated with the file changes. Every time mtime changes, ctime changes. However, ctime changes few extra times, for exmaple when you change the owner or the permission of the file. Can be read with ls -l (which is equivalent with ls -lc).
These values are returned in the file characteristics structure struct stat.
By default, ls lists last modification time (ctime).
Note that if the filesystem was mounted with "noatime" for performance reasons, then the atime will likely show the creation time. Given that "noatime" results in a massive performance boost (by removing a disk write for every time a file is read), it may be a sensible configuration option.
ls Time Commands
By default ls list the last status change time ctime (reflecting both data modification or metadata changes). It is equivalent with
ls -lc [--full-time] <my-file>
If we want it to list access time, use:
ls -lu [--full-time] <my-file>
Order files in the Descending Order of Last Changed Time
ls -lt *
To list just the file name without additional information:
ls -t *
The content of the directories is display. To avoid that, use -d.
Syntax Coloring
-G
It is equivalent with defining CLICOLOR in the environment (for Mac).
export CLICOLOR=cons25
LSCOLOR can provide more details on colors.
ls on Mac
@ at the end of the ls attribute output means the file has extend attributes. They can be listed with ls -l@ or xattr -l
Generate a Comma-Separated List with the Files and Sub-Directories
ls -m
This option can be used to reliably determine whether a directory is empty - the result will be the empty string.
Is the Directory Empty?
if [ -z "$(ls -m /tmp)" ]; then
echo "directory is empty"
fi