diff --git a/lib/portability.h b/lib/portability.h
index eadd99616..53b087046 100644
--- a/lib/portability.h
+++ b/lib/portability.h
@@ -247,6 +247,16 @@ static inline void endutxent(void) {;}
 #define O_PATH   010000000
 #endif
 
+// Glibc won't give you linux-kernel constants unless you say "no, a BUD lite"
+// even though linux has nothing to do with the FSF and never has.
+#ifndef F_SETPIPE_SZ
+#define F_SETPIPE_SZ 1031
+#endif
+
+#ifndef F_GETPIPE_SZ
+#define F_GETPIPE_SZ 1032
+#endif
+
 #if defined(__SIZEOF_DOUBLE__) && defined(__SIZEOF_LONG__) \
     && __SIZEOF_DOUBLE__ <= __SIZEOF_LONG__
 typedef double FLOAT;
diff --git a/toys/posix/ulimit.c b/toys/posix/ulimit.c
new file mode 100644
index 000000000..b14cd933b
--- /dev/null
+++ b/toys/posix/ulimit.c
@@ -0,0 +1,116 @@
+/* ulimit.c - Modify resource limits
+ *
+ * Copyright 2015 Rob Landley <rob@landley.net>
+ *
+ * See http://pubs.opengroup.org/onlinepubs/9699919799/utilities/ulimit.html
+ * And man prlimit(2).
+ *
+ * Deviations from posix: The units on -f are supposed to be 512 byte
+ * "blocks" (no other options are specified, and even hard drives don't
+ * do that anymore). Bash uses 1024 byte blocks, so they don't care either.
+ * We consistently use bytes everywhere we can.
+ *
+ * Deviations from bash: Sizes are in bytes (instead of -p 512 and -f 1024).
+ * Bash's -p value has been wrong since 2010 (git 35f3d14dbbc5).
+ * The kernel implementation of RLIMIT_LOCKS (-x) was removed from Linux in
+ * 2003. Bash never implemented -b (it's in the help but unrecognized at
+ * runtime). We support -P to affect processes other than us.
+
+USE_ULIMIT(NEWTOY(ulimit, ">1P#<1SHavutsrRqpnmlifedc[-SH][!apvutsrRqnmlifedc]", TOYFLAG_USR|TOYFLAG_BIN))
+
+config ULIMIT
+  bool "ulimit"
+  default y
+  help
+    usage: ulimit [-P PID] [-SHRacdefilmnpqrstuv] [LIMIT]
+
+    Print or set resource limits for process number PID. If no LIMIT specified
+    (or read-only -ap selected) display current value (sizes in bytes).
+    Default is ulimit -P $PPID -Sf" (show soft filesize of your shell).
+    
+    -S  Set/show soft limit          -H  Set/show hard (maximum) limit
+    -a  Show all limits              -c  Core file size
+    -d  Process data segment         -e  Max scheduling priority
+    -f  Output file size             -i  Pending signal count
+    -l  Locked memory                -m  Resident Set Size
+    -n  Number of open files         -p  Pipe buffer
+    -q  Posix message queue          -r  Max Real-time priority
+    -R  Realtime latency (usec)      -s  Stack size
+    -t  Total CPU time (in seconds)  -u  Maximum processes (under this UID)
+    -v  Virtual memory size          -P  PID to affect (default $PPID)
+*/
+
+#define FOR_ulimit
+#include "toys.h"
+
+GLOBALS(
+  long pid;
+)
+
+// This is a linux kernel syscall added in 2.6.36 (git c022a0acad53) which
+// glibc only exports a wrapper prototype for if you #define _FSF_HURD_RULZE.
+int prlimit(pid_t pid, int resource, const struct rlimit *new_limit,
+  struct rlimit *old_limit);
+
+// I'd like to sort the RLIMIT values 0-15, but mips, alpha and sparc
+// override the asm-generic values for 5-9. Also, the kernel implementation
+// of RLIMIT_LOCKS (-x) was removed from Linux in 2003.
+void ulimit_main(void)
+{
+  struct rlimit rr;
+  int i;
+  // Order is cdefilmnqRrstuv
+  char map[] = {RLIMIT_CORE, RLIMIT_DATA, RLIMIT_NICE, RLIMIT_FSIZE,
+                RLIMIT_SIGPENDING, RLIMIT_MEMLOCK, RLIMIT_RSS, RLIMIT_NOFILE, 0,
+                RLIMIT_MSGQUEUE, RLIMIT_RTTIME, RLIMIT_RTPRIO, RLIMIT_STACK,
+                RLIMIT_CPU, RLIMIT_NPROC, RLIMIT_AS};
+
+  if (!(toys.optflags&(FLAG_H-1))) toys.optflags |= FLAG_f;
+  if ((toys.optflags&(FLAG_a|FLAG_p)) && toys.optc) error_exit("can't set -ap");
+
+  // Fetch data
+  if (!(toys.optflags&FLAG_P)) TT.pid = getppid();
+
+  for (i=0; i<sizeof(map); i++) {
+    char *flags="cdefilmnpqRrstuv";
+
+    int get = toys.optflags&(FLAG_a|(1<<i));
+
+    if (get && prlimit(TT.pid, map[i], 0, &rr)) perror_exit("-%c", flags[i]);
+    if (!toys.optc) {
+      if (toys.optflags&FLAG_a) printf("-%c: ", flags[i]);
+      if (get) {
+        if ((1<<i)&FLAG_p) {
+          if (toys.optflags&FLAG_H)
+            xreadfile("/proc/sys/fs/pipe-max-size", toybuf, sizeof(toybuf));
+          else {
+            int pp[2];
+
+            xpipe(pp);
+            sprintf(toybuf, "%d\n", fcntl(*pp, F_GETPIPE_SZ));
+          }
+          printf("%s", toybuf);
+        } else {
+          rlim_t rl = (toys.optflags&FLAG_H) ? rr.rlim_max : rr.rlim_cur;
+
+          if (rl == RLIM_INFINITY) printf("unlimited\n");
+          else printf("%ld\n", (long)rl);
+        }
+      }
+    }
+    if (toys.optflags&(1<<i)) break;
+  }
+
+  if (toys.optflags&(FLAG_a|FLAG_p)) return;
+
+  if (toys.optc) {
+    rlim_t val;
+
+    if (tolower(**toys.optargs == 'i')) val = RLIM_INFINITY;
+    else val = atolx_range(*toys.optargs, 0, LONG_MAX);
+
+    if (toys.optflags&FLAG_H) rr.rlim_max = val;
+    else rr.rlim_cur = val;
+    if (prlimit(TT.pid, map[i], &rr, 0)) perror_exit(0);
+  }
+}