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chmod: Implement --dereference, -L, -H, etc
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Should fix tests/chmod/symlinks.sh
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@sylvestre
sylvestre committed Dec 30, 2024
1 parent ececf7d commit 05d59bf
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Showing 2 changed files with 326 additions and 9 deletions.
81 changes: 76 additions & 5 deletions src/uu/chmod/src/chmod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ use uucore::fs::display_permissions_unix;
use uucore::libc::mode_t;
#[cfg(not(windows))]
use uucore::mode;
use uucore::perms::TraverseSymlinks;
use uucore::{format_usage, help_about, help_section, help_usage, show, show_error};

const ABOUT: &str = help_about!("chmod.md");
Expand All @@ -33,6 +34,11 @@ mod options {
pub const RECURSIVE: &str = "recursive";
pub const MODE: &str = "MODE";
pub const FILE: &str = "FILE";
// TODO remove duplication with perms.rs
pub mod dereference {
pub const DEREFERENCE: &str = "dereference";
pub const NO_DEREFERENCE: &str = "no-dereference";
}
}

/// Extract negative modes (starting with '-') from the rest of the arguments.
Expand Down Expand Up @@ -99,7 +105,6 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
let quiet = matches.get_flag(options::QUIET);
let verbose = matches.get_flag(options::VERBOSE);
let preserve_root = matches.get_flag(options::PRESERVE_ROOT);
let recursive = matches.get_flag(options::RECURSIVE);
let fmode = match matches.get_one::<String>(options::REFERENCE) {
Some(fref) => match fs::metadata(fref) {
Ok(meta) => Some(meta.mode() & 0o7777),
Expand Down Expand Up @@ -138,6 +143,34 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
return Err(UUsageError::new(1, "missing operand".to_string()));
}

let mut dereference = if matches.get_flag(options::dereference::DEREFERENCE) {
Some(true) // Follow symlinks
} else if matches.get_flag(options::dereference::NO_DEREFERENCE) {
Some(false) // Do not follow symlinks
} else {
None // Default behavior
};

let mut traverse_symlinks = if matches.get_flag("L") {
TraverseSymlinks::All
} else if matches.get_flag("H") {
TraverseSymlinks::First
} else {
TraverseSymlinks::None
};

let recursive = matches.get_flag(options::RECURSIVE);
if recursive {
if traverse_symlinks == TraverseSymlinks::None {
if dereference == Some(true) {
return Err(USimpleError::new(1, "-R --dereference requires -H or -L"));
}
dereference = Some(false);
}
} else {
traverse_symlinks = TraverseSymlinks::None;
}

let chmoder = Chmoder {
changes,
quiet,
Expand All @@ -146,6 +179,8 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
recursive,
fmode,
cmode,
traverse_symlinks,
dereference: dereference.unwrap_or(true),
};

chmoder.chmod(&files)
Expand Down Expand Up @@ -237,6 +272,8 @@ struct Chmoder {
recursive: bool,
fmode: Option<u32>,
cmode: Option<String>,
traverse_symlinks: TraverseSymlinks,
dereference: bool,
}

impl Chmoder {
Expand All @@ -248,12 +285,19 @@ impl Chmoder {
let file = Path::new(filename);
if !file.exists() {
if file.is_symlink() {
if !self.dereference && !self.recursive {
// The file is a symlink and we should not follow it
// Don't try to change the mode of the symlink itself
continue;
}
if !self.quiet {
show!(USimpleError::new(
1,
format!("cannot operate on dangling symlink {}", filename.quote()),
));
set_exit_code(1);
}

if self.verbose {
println!(
"failed to change mode of {} from 0000 (---------) to 1500 (r-x-----T)",
Expand All @@ -273,6 +317,11 @@ impl Chmoder {
// So we set the exit code, because it hasn't been set yet if `self.quiet` is true.
set_exit_code(1);
continue;
} else if !self.dereference && file.is_symlink() {
// The file is a symlink and we should not follow it
// chmod 755 --no-dereference a/link
// should not change the permissions in this case
continue;
}
if self.recursive && self.preserve_root && filename == "/" {
return Err(USimpleError::new(
Expand All @@ -294,11 +343,23 @@ impl Chmoder {

fn walk_dir(&self, file_path: &Path) -> UResult<()> {
let mut r = self.chmod_file(file_path);
if !file_path.is_symlink() && file_path.is_dir() {
// Determine whether to traverse symlinks based on `self.traverse_symlinks`
let should_follow_symlink = match self.traverse_symlinks {
TraverseSymlinks::All => true,
TraverseSymlinks::First => {
file_path == file_path.canonicalize().unwrap_or(file_path.to_path_buf())
}
TraverseSymlinks::None => false,
};

// If the path is a directory (or we should follow symlinks), recurse into it
if (!file_path.is_symlink() || should_follow_symlink) && file_path.is_dir() {
for dir_entry in file_path.read_dir()? {
let path = dir_entry?.path();
if !path.is_symlink() {
r = self.walk_dir(path.as_path());
} else if should_follow_symlink {
r = self.chmod_file(path.as_path()).and(r);
}
}
}
Expand All @@ -316,17 +377,25 @@ impl Chmoder {
fn chmod_file(&self, file: &Path) -> UResult<()> {
use uucore::mode::get_umask;

let fperm = match fs::metadata(file) {
// Determine metadata based on dereference flag
let metadata = if self.dereference {
file.metadata() // Follow symlinks
} else {
file.symlink_metadata() // Act on the symlink itself
};

let fperm = match metadata {
Ok(meta) => meta.mode() & 0o7777,
Err(err) => {
if file.is_symlink() {
// Handle dangling symlinks or other errors
if file.is_symlink() && !self.dereference {
if self.verbose {
println!(
"neither symbolic link {} nor referent has been changed",
file.quote()
);
}
return Ok(());
return Ok(()); // Skip dangling symlinks
} else if err.kind() == std::io::ErrorKind::PermissionDenied {
// These two filenames would normally be conditionally
// quoted, but GNU's tests expect them to always be quoted
Expand All @@ -339,6 +408,8 @@ impl Chmoder {
}
}
};

// Determine the new permissions to apply
match self.fmode {
Some(mode) => self.change_file(fperm, mode, file)?,
None => {
Expand Down
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