Add LibC.setrlimit/LibC.getrlimit to all linux/bsd platforms

spec/std/system_spec.cr

@@ -23,4 +23,25 @@ describe System do
       cpu_count.should eq(shell_cpus)
     end
   end
+
+  pending_win32 describe: "file_descriptor_limit" do
+    it "returns the current file descriptor limit" do
+      hard_fd_limit = `ulimit -Hn`.strip
+      $?.success?.should be_true
+      soft_fd_limit = `ulimit -Sn`.strip
+      $?.success?.should be_true
+
+      soft_limit, hard_limit = System.file_descriptor_limit
+      hard_limit.to_s.should eq hard_fd_limit
+      soft_limit.to_s.should eq soft_fd_limit
+    end
+
+    it "can set the limit" do
+      System.file_descriptor_limit = 512
+
+      soft_fd_limit = `ulimit -Sn`.strip
+      $?.success?.should be_true
+      soft_fd_limit.should eq "512"
+    end
+  end
 end

src/crystal/system.cr

@@ -10,6 +10,7 @@ end
 
 {% if flag?(:unix) %}
   require "./system/unix/hostname"
+  require "./system/unix/file_descriptor_limit"
 
   {% if flag?(:bsd) %}
     require "./system/unix/sysctl_cpucount"

src/crystal/system/unix/file_descriptor_limit.cr

@@ -0,0 +1,18 @@
+module Crystal::System
+  def self.file_descriptor_limit : Tuple(Int32, Int32)
+    rlimit = uninitialized LibC::Rlimit
+    if LibC.getrlimit(LibC::RLIMIT_NOFILE, pointerof(rlimit)) != 0
+      raise RuntimeError.from_errno("Could not get rlimit")
+    end
+    {rlimit.rlim_cur.to_i32, rlimit.rlim_max.to_i32}
+  end
+
+  def self.file_descriptor_limit=(limit : Int) : Nil
+    rlimit = LibC::Rlimit.new
+    rlimit.rlim_cur = limit
+    rlimit.rlim_max = limit
+    if LibC.setrlimit(LibC::RLIMIT_NOFILE, pointerof(rlimit)) != 0
+      raise RuntimeError.from_errno("Could not set rlimit")
+    end
+  end
+end

src/crystal/system/win32/file_descriptor_limit.cr

@@ -0,0 +1,9 @@
+module Crystal::System
+  def self.file_descriptor_limit : Tuple(Int32, Int32)
+    raise NotImplementedError.new
+  end
+
+  def self.file_descriptor_limit=(limit : Int) : Nil
+    raise NotImplementedError.new
+  end
+end

src/lib_c/aarch64-darwin/c/sys/resource.cr

@@ -7,8 +7,10 @@ lib LibC
   end
 
   fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
 
-  RLIMIT_STACK = 3
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 7
 
   struct RUsage
     ru_utime : Timeval

src/lib_c/aarch64-linux-gnu/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 7
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/lib_c/aarch64-linux-musl/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 7
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/lib_c/arm-linux-gnueabihf/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 7
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/lib_c/i386-linux-gnu/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 7
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/lib_c/i386-linux-musl/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 7
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/lib_c/x86_64-darwin/c/sys/resource.cr

@@ -7,8 +7,10 @@ lib LibC
   end
 
   fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
 
-  RLIMIT_STACK = 3
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 7
 
   struct RUsage
     ru_utime : Timeval

src/lib_c/x86_64-dragonfly/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 8
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/lib_c/x86_64-freebsd/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 8
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/lib_c/x86_64-linux-gnu/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 7
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/lib_c/x86_64-linux-musl/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 7
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/lib_c/x86_64-netbsd/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 8
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/lib_c/x86_64-openbsd/c/sys/resource.cr

@@ -1,4 +1,17 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+  fun setrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK  = 3
+  RLIMIT_NOFILE = 8
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval

src/system.cr

@@ -22,4 +22,22 @@ module System
   def self.cpu_count
     Crystal::System.cpu_count
   end
+
+  # Returns the soft and hard file descriptor limits for the current process
+  #
+  # ```
+  # System.file_descriptor_limit # => { 1024, 524288 }
+  # ```
+  def self.file_descriptor_limit
+    Crystal::System.file_descriptor_limit
+  end
+
+  # Sets the soft file descriptor limits for the current process
+  #
+  # ```
+  # System.file_descriptor_limit = 4096
+  # ```
+  def self.file_descriptor_limit=(limit : UInt32)
+    Crystal::System.file_descriptor_limit = limit
+  end
 end