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const std = @import("std");
fn isValid(buf: *[std.fs.MAX_PATH_BYTES]u8, segment: []const u8, bin: []const u8) ?u16 {
std.mem.copy(u8, buf, segment);
buf[segment.len] = std.fs.path.sep;
std.mem.copy(u8, buf[segment.len + 1 ..], bin);
buf[segment.len + 1 + bin.len ..][0] = 0;
const filepath = buf[0 .. segment.len + 1 + bin.len :0];
var stat = std.mem.zeroes(std.os.Stat);
// we cannot use access() here even though all we want to do now here is check it is executable
// directories can be considered executable
std.os.accessZ(filepath, std.os.X_OK) catch return null;
return @intCast(u16, filepath.len);
}
// Like /usr/bin/which but without needing to exec a child process
// Remember to resolve the symlink if necessary
pub fn which(buf: *[std.fs.MAX_PATH_BYTES]u8, path: []const u8, cwd: []const u8, bin: []const u8) ?[:0]const u8 {
if (isValid(buf, std.mem.trimRight(u8, cwd, std.fs.path.sep_str), bin)) |len| {
return buf[0..len :0];
}
var path_iter = std.mem.tokenize(u8, path, ":");
while (path_iter.next()) |segment| {
if (isValid(buf, segment, bin)) |len| {
return buf[0..len :0];
}
}
return null;
}
test "which" {
var buf: [std.fs.MAX_PATH_BYTES]u8 = undefined;
var realpath = std.os.getenv("PATH") orelse unreachable;
var whichbin = which(&buf, realpath, try std.process.getCwdAlloc(std.heap.c_allocator), "which");
try std.testing.expectEqualStrings(whichbin orelse return std.debug.assert(false), "/usr/bin/which");
try std.testing.expect(null == which(&buf, realpath, try std.process.getCwdAlloc(std.heap.c_allocator), "baconnnnnn"));
try std.testing.expect(null != which(&buf, realpath, try std.process.getCwdAlloc(std.heap.c_allocator), "zig"));
try std.testing.expect(null == which(&buf, realpath, try std.process.getCwdAlloc(std.heap.c_allocator), "bin"));
try std.testing.expect(null == which(&buf, realpath, try std.process.getCwdAlloc(std.heap.c_allocator), "usr"));
}
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