Bash — Files

File types

#!/bin/bash

file="test.txt"

[ -f "$file" ] && echo "Regular file"
[ -d "$file" ] && echo "Directory"
[ -L "$file" ] && echo "Symbolic link"
[ -r "$file" ] && echo "Readable"
[ -w "$file" ] && echo "Writable"
[ -x "$file" ] && echo "Executable"
[ -s "$file" ] && echo "Non-empty"

Creating files

#!/bin/bash

# Touch (create or update timestamp)
touch file.txt

# Echo to file
echo "Hello" > file.txt

# Cat with heredoc
cat > file.txt << EOF
Line 1
Line 2
Line 3
EOF

Reading files

#!/bin/bash

# Entire file
content=$(cat file.txt)

# Line by line
while IFS= read -r line; do
    echo "$line"
done < file.txt

# With line numbers
nl file.txt

Permissions

#!/bin/bash

chmod +x script.sh     # Make executable
chmod 755 script.sh    # rwxr-xr-x
chmod 644 file.txt     # rw-r--r--
chown user:group file  # Change owner

Symbolic links

#!/bin/bash

ln -s /path/to/original link_name  # Create symlink
ls -l link_name                     # View symlink

Mini Practice

Write Bash code that:

1. Checks file type and permissions
2. Creates and reads a file
3. Changes file permissions
4. Creates a symbolic link

Up Next

In the next lesson, you'll learn about Directories — directory operations.