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BCH709 Introduction to Bioinformatics: Symbolic Links

Symbolic links (symlinks) are shortcuts that point to other files or directories.

# Create a test file
echo "Original content" > original_file.txt
cat original_file.txt

Original content

# Create a symbolic link
ln -s original_file.txt my_shortcut.txt

# View the link (note the -> arrow)
ls -l my_shortcut.txt

lrwxrwxrwx 1 user group 17 Jan 20 10:00 my_shortcut.txt -> original_file.txt

# Access through the link
cat my_shortcut.txt

Original content

# Modify through the link
echo "Added via link" >> my_shortcut.txt

# Original file is modified!
cat original_file.txt

Original content
Added via link

# Delete original - link becomes broken
rm original_file.txt
cat my_shortcut.txt

cat: my_shortcut.txt: No such file or directory

# Link still exists but is broken (red in colored ls)
ls -l my_shortcut.txt

lrwxrwxrwx 1 user group 17 Jan 20 10:00 my_shortcut.txt -> original_file.txt
Feature Symbolic Link Hard Link
Command ln -s target link ln target link
Link to directories Yes No
Original deleted Link breaks Link works
Cross filesystems Yes No 
# Create files to compare
echo "test" > testfile.txt
ln -s testfile.txt symlink.txt    # Symbolic
ln testfile.txt hardlink.txt      # Hard

# Check inode numbers (-i flag)
ls -li testfile.txt symlink.txt hardlink.txt

123456 -rw-r--r-- 2 user group 5 Jan 20 testfile.txt
123457 lrwxrwxrwx 1 user group 12 Jan 20 symlink.txt -> testfile.txt
123456 -rw-r--r-- 2 user group 5 Jan 20 hardlink.txt

Note: hardlink.txt has the SAME inode (123456) as testfile.txt