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const std = @import("std");
const builtin = @import("builtin");
const Allocator = std.mem.Allocator;
const testing = std.testing;
/// Search for "cmd" in the PATH and return the absolute path. This will
/// always allocate if there is a non-null result. The caller must free the
/// resulting value.
pub fn expand(alloc: Allocator, cmd: []const u8) !?[]u8 {
// If the command already contains a slash, then we return it as-is
// because it is assumed to be absolute or relative.
if (std.mem.indexOfScalar(u8, cmd, '/') != null) {
return try alloc.dupe(u8, cmd);
}
const PATH = switch (builtin.os.tag) {
.windows => blk: {
const win_path = std.process.getenvW(std.unicode.utf8ToUtf16LeStringLiteral("PATH")) orelse return null;
const path = try std.unicode.utf16LeToUtf8Alloc(alloc, win_path);
break :blk path;
},
else => std.posix.getenvZ("PATH") orelse return null,
};
defer if (builtin.os.tag == .windows) alloc.free(PATH);
var path_buf: [std.fs.max_path_bytes]u8 = undefined;
var it = std.mem.tokenizeScalar(u8, PATH, std.fs.path.delimiter);
var seen_eacces = false;
while (it.next()) |search_path| {
// We need enough space in our path buffer to store this
const path_len = search_path.len + cmd.len + 1;
if (path_buf.len < path_len) return error.PathTooLong;
// Copy in the full path
@memcpy(path_buf[0..search_path.len], search_path);
path_buf[search_path.len] = std.fs.path.sep;
@memcpy(path_buf[search_path.len + 1 ..][0..cmd.len], cmd);
path_buf[path_len] = 0;
const full_path = path_buf[0..path_len :0];
// Stat it
const f = std.fs.cwd().openFile(
full_path,
.{},
) catch |err| switch (err) {
error.FileNotFound => continue,
error.AccessDenied => {
// Accumulate this and return it later so we can try other
// paths that we have access to.
seen_eacces = true;
continue;
},
else => return err,
};
defer f.close();
const stat = try f.stat();
if (stat.kind != .directory and isExecutable(stat.mode)) {
return try alloc.dupe(u8, full_path);
}
}
if (seen_eacces) return error.AccessDenied;
return null;
}
fn isExecutable(mode: std.fs.File.Mode) bool {
if (builtin.os.tag == .windows) return true;
return mode & 0o0111 != 0;
}
// `uname -n` is the *nix equivalent of `hostname.exe` on Windows
test "expand: hostname" {
const executable = if (builtin.os.tag == .windows) "hostname.exe" else "uname";
const path = (try expand(testing.allocator, executable)).?;
defer testing.allocator.free(path);
try testing.expect(path.len > executable.len);
}
test "expand: does not exist" {
const path = try expand(testing.allocator, "thisreallyprobablydoesntexist123");
try testing.expect(path == null);
}
test "expand: slash" {
const path = (try expand(testing.allocator, "foo/env")).?;
defer testing.allocator.free(path);
try testing.expect(path.len == 7);
}
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