[module]
name = "chmod"
description = "Change file permissions"
version = 1
[intro]
text = """
## What is chmod?
`chmod` (change mode) modifies the read/write/execute permissions of files and directories.
## Permission Model
Each file has three permission sets:
- **u** — user (owner)
- **g** — group
- **o** — others (everyone else)
- **a** — all three at once
Each set has three bits:
- **r** (read) = 4
- **w** (write) = 2
- **x** (execute) = 1
## Symbolic vs Numeric
**Symbolic:** `chmod u+x file` (add execute for user)
**Numeric:** `chmod 755 file` (rwxr-xr-x — user=7, group=5, others=5)
## Common Patterns
- `chmod +x script.sh` — make executable
- `chmod 644 file.txt` — owner read/write, group/others read-only
- `chmod 755 dir/` — owner full access, group/others read+execute
- `chmod -R g-w dir/` — remove group write recursively
"""
[[examples]]
title = "Make a script executable"
description = "Add execute permission for all users"
command = "chmod +x deploy.sh && find . -name 'deploy.sh' -perm -u+x"
output = "./deploy.sh\n"
[[examples]]
title = "Set numeric permissions"
description = "Set rw-r--r-- (owner read+write, others read-only)"
command = "chmod 644 config.txt && find . -name 'config.txt' -perm 644"
output = "./config.txt\n"
[[exercises]]
id = "chmod.1"
difficulty = "beginner"
question = """The file `script.sh` exists but is not executable.
Make it executable by the owner and verify using find."""
expected_output = "./script.sh\n"
hints = [
"Use chmod +x to add execute permission",
"Verify with: find . -name 'script.sh' -perm -u+x",
"Try: chmod +x script.sh && find . -name 'script.sh' -perm -u+x",
]
solution = "chmod +x script.sh && find . -name 'script.sh' -perm -u+x"
match_mode = "exact"
[[exercises.fixtures]]
filename = "script.sh"
content = "#!/bin/sh\necho hello\n"
[[exercises]]
id = "chmod.2"
difficulty = "beginner"
question = """The file `config.txt` currently has wide-open permissions.
Set it to 644 (owner read+write, everyone else read-only) and verify."""
expected_output = "./config.txt\n"
hints = [
"Use numeric mode: chmod 644",
"Verify with: find . -name 'config.txt' -perm 644",
"Try: chmod 644 config.txt && find . -name 'config.txt' -perm 644",
]
solution = "chmod 644 config.txt && find . -name 'config.txt' -perm 644"
match_mode = "exact"
[[exercises.fixtures]]
filename = "config.txt"
content = "key=value\n"
[[exercises]]
id = "chmod.3"
difficulty = "beginner"
question = """The file `secret.txt` should be readable and writable only by the owner (mode 600).
Set it and verify."""
expected_output = "./secret.txt\n"
hints = [
"Mode 600 = rw------- (owner read+write, no access for group/others)",
"Try: chmod 600 secret.txt && find . -name 'secret.txt' -perm 600",
]
solution = "chmod 600 secret.txt && find . -name 'secret.txt' -perm 600"
match_mode = "exact"
[[exercises.fixtures]]
filename = "secret.txt"
content = "password=hunter2\n"
[[exercises]]
id = "chmod.4"
difficulty = "intermediate"
question = """All three `.sh` files in the current directory need to be executable.
Make them all executable in one command and verify by listing them with find."""
expected_output = "./build.sh\n./deploy.sh\n./test.sh\n"
hints = [
"Use a glob with chmod, then find -perm -u+x",
"Try: chmod +x *.sh && find . -name '*.sh' -perm -u+x",
]
solution = "chmod +x *.sh && find . -name '*.sh' -perm -u+x"
match_mode = "sorted"
[[exercises.fixtures]]
filename = "build.sh"
content = "#!/bin/sh\necho build\n"
[[exercises.fixtures]]
filename = "deploy.sh"
content = "#!/bin/sh\necho deploy\n"
[[exercises.fixtures]]
filename = "test.sh"
content = "#!/bin/sh\necho test\n"
[[exercises]]
id = "chmod.5"
difficulty = "intermediate"
question = """The directory `private/` and everything inside it should deny access to group and others.
Use chmod -R to set mode 700 recursively and verify the directory itself."""
expected_output = "./private\n"
hints = [
"Use chmod -R 700 to set permissions recursively",
"Verify with: find . -name 'private' -perm 700 -type d",
"Try: chmod -R 700 private && find . -name 'private' -perm 700 -type d",
]
solution = "chmod -R 700 private && find . -name 'private' -perm 700 -type d"
match_mode = "exact"
[[exercises.fixtures]]
filename = "private/notes.txt"
content = "secret notes\n"
[[exercises.fixtures]]
filename = "private/data.txt"
content = "secret data\n"
[[exercises]]
id = "chmod.6"
difficulty = "advanced"
question = """The file `shared.txt` should allow the owner to read and write, the group to read only, and deny all access to others (mode 640).
Set permissions and verify."""
expected_output = "./shared.txt\n"
hints = [
"Mode 640 = rw-r----- (user=6, group=4, others=0)",
"Try: chmod 640 shared.txt && find . -name 'shared.txt' -perm 640",
]
solution = "chmod 640 shared.txt && find . -name 'shared.txt' -perm 640"
match_mode = "exact"
[[exercises.fixtures]]
filename = "shared.txt"
content = "shared content\n"