DevOps AcademyLearn the delivery system
Chapter 03Lesson 02~45 minutes

Navigating with pwd, cd, ls, and tree

Filesystem navigation is not merely moving between folders. DevOps work depends on knowing exactly which directory a command will affect, which entries are hidden, and how to create evidence before changing files.

BeginnerFilesystemHands-on lab

Learning objectives

By the end of this lesson

  • Explain the current working directory and how processes inherit it.
  • Navigate with pwd and cd using explicit, home-relative, and previous-directory targets.
  • Interpret long listings, hidden entries, timestamps, ownership, and file-type indicators.
  • Use tree or find to produce a bounded directory map.
  • Build a repeatable course workspace and verify every navigation step.

1. Every process has a current working directory

A Linux path can be resolved relative to a process’s current working directory. Your interactive shell maintains its own working directory. Commands launched by that shell normally inherit it, which is why running the same relative command from two directories can affect different files.

How a relative command target is resolved 
flowchart TD
  S["Shell current directory"] --> R["Relative path argument"]
  R --> N["Kernel pathname resolution"]
  A["Absolute path argument"] --> N
  N --> I["Resolved filesystem object"]
  I --> C["Command reads or changes target"]
Operational rule

Before a command that copies, removes, changes permissions, installs, builds, or deploys, print and verify the working directory. A correct command in the wrong directory is still a failure.

2. Confirm location with pwd

pwd prints the shell’s current working directory. Bash also maintains $PWD and $OLDPWD. The logical view can preserve symbolic-link components, while the physical view resolves them. 

printf 'PWD variable: %s\n' "$PWD"
printf 'Logical path: '
pwd -L
printf 'Physical path: '
pwd -P
printf 'Previous directory: %s\n' "${OLDPWD-not set}"
FormMeaningUse
pwdPrint current path using shell/default behaviorRoutine orientation
pwd -LLogical path, potentially retaining symbolic-link namesMatches the path through which the user navigated
pwd -PPhysical path with symbolic links resolvedVerifying the underlying directory target

3. Change location with cd

cd must be a shell built-in because an external process cannot permanently change its parent shell’s working directory. The command accepts absolute or relative paths and several useful conventions.

CommandDestinationOperational note
cdYour home directoryEquivalent to a valid cd "$HOME"
cd /var/logAbsolute directoryIndependent of current location
cd ..Parent directoryResolved from the current location
cd -Previous working directoryUses $OLDPWD and normally prints the destination
cd -- "$target"Directory stored in a variableQuoting and -- protect unusual names 
start=$PWD
cd -- "$HOME"
printf 'Home: %s\n' "$PWD"
cd -- "$start"
printf 'Returned: %s\n' "$PWD"

# Bash directory-stack commands are useful for temporary jumps.
pushd /tmp >/dev/null
printf 'Temporary location: %s\n' "$PWD"
popd >/dev/null
printf 'Restored location: %s\n' "$PWD"

4. List directory entries with ls

ls shows names by default. Operational work often needs hidden entries, ownership, permissions, sizes, timestamps, and unambiguous escaping. Options can vary between implementations, so use ls --help or man ls on the target system. 

# Names, including hidden entries other than . and ..
ls -A

# Long listing with human-readable sizes
ls -lhA

# Sort newest modification time first
ls -lt

# Show inode numbers and classify common file types
ls -liF

# Quote unusual names so whitespace and control characters are visible
ls -lb
Hidden does not mean protected

A filename beginning with a dot is omitted by default from many listings. It has no special security protection. Configuration, credentials, caches, and repository metadata often use dot-prefixed names.

5. Read a long listing correctly

drwxr-xr-x 2 learner devops 4096 Aug  4 10:15 scripts
-rw-r----- 1 learner devops  842 Aug  4 10:14 deploy.env
lrwxrwxrwx 1 learner devops   11 Aug  4 10:16 current -> releases/v2
01Type and permissions

The first character distinguishes a directory, regular file, symbolic link, and other object types. The remaining characters summarize permission bits.

02Link count

The next field counts hard links to the inode; directories reflect subdirectory relationships.

03Owner and group

These identities interact with permission bits and access-control rules.

04Size and timestamp

The meaning of size depends on object type. The displayed timestamp is usually modification time unless options select another.

05Name and link target

Symbolic links display their stored target after an arrow.

6. Map a hierarchy with tree or find

tree is a convenient optional package, not guaranteed to be installed. Limit depth and entry count when inspecting large repositories or system directories. 

target="$HOME/devops-academy"

if command -v tree >/dev/null 2>&1; then
  tree -a -L 3 --dirsfirst -- "$target"
else
  printf 'tree is unavailable; using find instead\n' >&2
  find "$target" -maxdepth 3 -printf '%y %p\n' | sort
fi

A directory map is evidence, not a substitute for metadata. Use stat, file, permissions tools, and content inspection when the object’s exact nature matters.

7. Navigation patterns for automation

Fail explicitly

Guard every required cd

Use cd -- "$target" || exit in simple scripts, or return an error from a function. Never continue silently from the wrong directory.

Prefer explicit roots

Build paths from known variables

Use an established workspace root rather than chains of fragile ../../.. references.

Quote paths

Preserve whitespace and special characters

cd -- "$path" prevents splitting and option confusion.

Verify before change

Print resolved context

Capture pwd -P, directory metadata, and target lists before bulk operations.

8. Hands-on lab: build and map a course workspace

root="$HOME/devops-academy/linux/chapter03/lesson02"
mkdir -p -- \
  "$root/projects/api/config" \
  "$root/projects/web/public" \
  "$root/runbooks" \
  "$root/.state"

printf 'environment=lab\n' > "$root/projects/api/config/app.env"
printf '# Recovery runbook\n' > "$root/runbooks/recovery.md"
printf 'created=%s\n' "$(date --iso-8601=seconds 2>/dev/null || date)" > "$root/.state/manifest"

cd -- "$root" || exit 1
printf 'logical=%s\n' "$(pwd -L)"
printf 'physical=%s\n' "$(pwd -P)"

printf '\nTop-level entries, including hidden state:\n'
ls -lah

printf '\nBounded workspace map:\n'
if command -v tree >/dev/null 2>&1; then
  tree -a -L 4 --dirsfirst .
else
  find . -maxdepth 4 -printf '%y %p\n' | sort
fi

printf '\nRound trip with cd -:\n'
cd projects/api
pwd
cd -
pwd

Verification checklist

9. Common navigation mistakes

Running a destructive command after a failed cd

If navigation fails and a script continues, a relative target can resolve in the old directory. Stop immediately on required navigation failure.

Assuming ls shows everything

Dot-prefixed entries are omitted unless requested. Important repository and configuration state may be hidden.

Parsing default ls output in scripts

Human-oriented formatting and unusual filenames make it unreliable. Prefer find, shell globs, or machine-readable interfaces.

Using deep relative paths without context

Long chains of parent references are difficult to review. Establish a known root and derive targets from it.

10. Knowledge check

Question 1. Why must cd be implemented by the shell?

Question 2. What is the difference between pwd -L and pwd -P?

Question 3. Why is a default ls listing insufficient before many operations?

11. Summary

The shell’s working directory is inherited by commands and controls how relative paths resolve. Use pwd to establish context, cd with checked and quoted targets, ls to inspect metadata and hidden entries, and tree or bounded find output to map a hierarchy. Verification belongs before every consequential file operation.

Next lesson

Absolute Paths, Relative Paths, and Path Expansion

You will examine how Linux resolves path components and how the shell transforms path expressions before a command receives them.

12. Further reading

  • GNU Coreutils documentation for pwd, ls, and directory operations.
  • GNU Bash Reference Manual — Bourne shell built-ins, directory stack, variables, and shell parameters.
  • Linux manual pages for chdir, getcwd, stat, find, and tree when installed.
  • Filesystem Hierarchy Standard — conventional system directory purposes.
  • POSIX specifications for cd, pwd, and pathname resolution.

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