btrfs_cli/property/
get.rs

1use super::{PropertyObjectType, detect_object_types, property_names};
2use crate::{RunContext, Runnable, util::open_path};
3use anyhow::{Context, Result, anyhow, bail};
4use btrfs_uapi::{filesystem::label_get, subvolume::subvolume_flags_get};
5use clap::Parser;
6use std::{
7    fs::File,
8    os::unix::io::AsFd,
9    path::{Path, PathBuf},
10};
11
12/// Get a property value of a btrfs object
13///
14/// If no name is specified, all properties for the object are printed.
15#[derive(Parser, Debug)]
16pub struct PropertyGetCommand {
17    /// Object type (inode, subvol, filesystem, device)
18    #[clap(short = 't', long = "type")]
19    pub object_type: Option<PropertyObjectType>,
20
21    /// Path to the btrfs object
22    pub object: PathBuf,
23
24    /// Property name to retrieve
25    pub name: Option<String>,
26}
27
28impl Runnable for PropertyGetCommand {
29    fn run(&self, _ctx: &RunContext) -> Result<()> {
30        let file = open_path(&self.object)?;
31
32        // Detect object type if not specified
33        let detected_types = detect_object_types(&self.object);
34        let target_type = if let Some(t) = self.object_type {
35            t
36        } else {
37            // If ambiguous, require the user to specify
38            if detected_types.len() > 1 {
39                bail!(
40                    "object type is ambiguous, please use option -t (detected: {detected_types:?})"
41                );
42            }
43            detected_types
44                .first()
45                .copied()
46                .ok_or_else(|| anyhow!("object is not a btrfs object"))?
47        };
48
49        // If a specific property is requested, get it
50        if let Some(name) = &self.name {
51            get_property(&file, target_type, name, &self.object)?;
52        } else {
53            // Otherwise, list all properties with their values
54            for name in property_names(target_type) {
55                // Best-effort: print what we can, skip errors for individual properties
56                let _ = get_property(&file, target_type, name, &self.object);
57            }
58        }
59
60        Ok(())
61    }
62}
63
64fn get_property(
65    file: &File,
66    obj_type: PropertyObjectType,
67    name: &str,
68    path: &Path,
69) -> Result<()> {
70    match (obj_type, name) {
71        (PropertyObjectType::Subvol, "ro") => {
72            let flags =
73                subvolume_flags_get(file.as_fd()).with_context(|| {
74                    format!(
75                        "failed to get read-only flag for '{}'",
76                        path.display()
77                    )
78                })?;
79            let is_readonly =
80                flags.contains(btrfs_uapi::subvolume::SubvolumeFlags::RDONLY);
81            println!("ro={}", if is_readonly { "true" } else { "false" });
82        }
83        (
84            PropertyObjectType::Filesystem | PropertyObjectType::Device,
85            "label",
86        ) => {
87            let label = label_get(file.as_fd()).with_context(|| {
88                format!("failed to get label for '{}'", path.display())
89            })?;
90            println!("label={}", label.to_bytes().escape_ascii());
91        }
92        (PropertyObjectType::Inode, "compression") => {
93            get_compression_property(file, path)?;
94        }
95        _ => {
96            bail!(
97                "property '{name}' is not applicable to object type {obj_type:?}"
98            );
99        }
100    }
101
102    Ok(())
103}
104
105fn get_compression_property(file: &File, path: &Path) -> Result<()> {
106    use nix::libc::{ENODATA, fgetxattr};
107    use std::os::unix::io::AsRawFd;
108
109    let fd = file.as_raw_fd();
110    let xattr_name = "btrfs.compression\0";
111
112    // SAFETY: fgetxattr is safe to call with a valid fd and valid string pointer
113    let result = unsafe {
114        fgetxattr(fd, xattr_name.as_ptr().cast(), std::ptr::null_mut(), 0)
115    };
116
117    if result < 0 {
118        let errno = nix::errno::Errno::last_raw();
119        if errno == ENODATA {
120            // Attribute doesn't exist; compression not set
121            return Ok(());
122        }
123        return Err(anyhow::anyhow!(
124            "failed to get compression for '{}': {}",
125            path.display(),
126            nix::errno::Errno::from_raw(errno)
127        ));
128    }
129
130    #[allow(clippy::cast_sign_loss)] // result is positive after the check above
131    let len = result as usize;
132    let mut buf = vec![0u8; len];
133
134    // SAFETY: fgetxattr is safe to call with a valid fd, valid buffer, and valid string pointer
135    let result = unsafe {
136        fgetxattr(fd, xattr_name.as_ptr().cast(), buf.as_mut_ptr().cast(), len)
137    };
138
139    if result < 0 {
140        return Err(anyhow::anyhow!(
141            "failed to get compression for '{}'",
142            path.display()
143        ));
144    }
145
146    let value = String::from_utf8_lossy(&buf);
147    println!("compression={value}");
148
149    Ok(())
150}
btrfs_cli/property/get.rs

btrfs_cli/property/
get.rs
