When working on automation scripts or organizing large datasets, you often need to create sequential folders like 00-99 across multiple locations. Doing this manually would be:


Time-consuming for hundreds of directories
Error-prone when creating 100 folders each time
Inconsistent in naming patterns




Bash's brace expansion feature lets you generate sequences with a single command:

mkdir -p {00..99}

Breaking this down:

mkdir: The directory creation command
-p: No error if existing (useful when re-running)
{00..99}: Generates zero-padded numbers 00 through 99

Case 1: Creating in current directory
# Simple creation
mkdir {00..99}

Case 2: Creating with specific permissions
mkdir -m 755 {00..99}  # Sets rwxr-xr-x permissions

Case 3: Creating in multiple target directories
target_dirs=("/data/project1" "/backups/project2")
for dir in "${target_dirs[@]}"; do
  mkdir -p "${dir}"/{00..99}
done

When implementing in scripts, consider:
# Check if parent directory exists first
parent_dir="/path/to/parent"
if [ -d "$parent_dir" ]; then
  mkdir -p "${parent_dir}"/{00..99}
else
  echo "Error: Parent directory missing" >&2
  exit 1
fi

For creating across hundreds of locations, this approach is:

Faster than 100 separate mkdir commands
More memory-efficient than loop implementations
Atomic in execution (all succeed or none)



Method
Pros
Cons


Brace Expansion
Simplest syntax, native to bash
Bash-specific


seq + xargs
More portable
Complexer syntax


printf + loop
Maximum control
Verbose


Example using seq:
seq -w 0 99 | xargs mkdir

In my recent data pipeline project, I used this technique to:
# Create folder structure for daily snapshots
for year in {2020..2023}; do
  mkdir -p "/data/archive/${year}"/{01..12}/{00..31}
done

This created 4,464 directories (4 years × 12 months × 31 days) with perfect zero-padding.


When managing large-scale file systems, you might need to create structured directory trees with numbered folders ranging from 00 to 99 across multiple locations. Doing this manually would be incredibly time-consuming and error-prone.
Here's the most efficient way to accomplish this in Ubuntu/Linux:
mkdir -p {00..99}
Let's examine why this works:

mkdir: The standard directory creation command
-p: Ensures no error if folders exist (helpful for repeated runs)
{00..99}: Bash brace expansion that generates two-digit numbers

For creating these folders in multiple locations:
target_dirs=("/path1" "/path2" "/path3")
for dir in "${target_dirs[@]}"; do
    mkdir -p "$dir"/{00..99}
done
To verify successful creation and count folders:
ls -d */ | wc -l
For systems with limited bash features, use seq:
for i in $(seq -w 0 99); do
    mkdir -p "$i"
done