Change the interface to lam_few() -- add a "int *status" argument to pass

back the status from the child process.  The return type is now an int
indicating whether the few was successful or not; if it wasn't, the
exact error will be in errno.

This commit was SVN r251.

src/lam/util/few.c

@@ -2,44 +2,85 @@
  * $HEADER$
  */
 
+#include "lam_config.h"
+
 #include <stdio.h>
 #include <errno.h>
 #include <sys/wait.h>
 #include <stdlib.h>
 #include <unistd.h>
 
-#include "lam_config.h"
+#include "lam/constants.h"
 #include "lam/util/few.h"
 
 /** @file **/
 
 /**
- *  forks, execs and waits for a subordinate program
+ *  Forks, execs, and waits for a subordinate program
  *
- *  @param argv Argument vector, argv[0] is the program
- *  @retval Status code or ERROR
- *  Returns:    - status code or ERROR
+ * @param argv Null-terminated argument vector; argv[0] is the program
+ * (same as arguments to execvp())
+ *
+ * @param status Upon success, will be filled with the return status
+ * from waitpid(2).  The WIF* macros can be used to examine the value
+ * (see waitpid(2)).
+ *
+ * @retval LAM_SUCCESS If the child launched and exited.
+ * @retval LAM_ERR_IN_ERRNO If a failure occurred, errno should be
+ * examined for the specific error.
+ *
+ * This function forks, execs, and waits for an executable to
+ * complete.  The input argv must be a NULL-terminated array (perhaps
+ * built with the lam_arr_*() interface).  Upon success, LAM_SUCCESS
+ * is returned.  This function will wait either until the child
+ * process has exited or waitpid() returns an error other than EINTR.
+ *
+ * Note that a return of LAM_SUCCESS does \em not imply that the child
+ * process exited successfully -- it simply indicates that the child
+ * process exited.  The WIF* macros (see waitpid(2)) should be used to
+ * examine the status to see hold the child exited.
  */
 int
-lam_few(char *argv[])
+lam_few(char *argv[], int *status)
 {
-    int status;
-    int pid;
-    int ret;
+    pid_t pid, ret;
 
     if ((pid = fork()) < 0) {
-        return(pid);
-        }
-    /* child */
-    else if (0 == pid) {    
-        execvp(argv[0], argv);
-        exit(errno);
-        }
-    /* parent */
-    else {  
-        while ((0 != waitpid(pid, &status, 0)) &&
-                (! WIFEXITED(status)) && (EINTR == errno));
+      return LAM_ERR_IN_ERRNO;
     }
 
-    return status;
+    /* Child execs.  If it fails to exec, exit. */
+
+    else if (0 == pid) {    
+      execvp(argv[0], argv);
+      exit(errno);
+    }
+
+    /* Parent loops waiting for the child to die. */
+
+    else {  
+      do {
+        /* If the child exited, return */
+
+        if (pid == (ret = waitpid(pid, status, 0))) {
+          break;
+        } 
+
+        /* If waitpid was interrupted, loop around again */
+
+        else if (ret < 0) {
+          if (EINTR == errno) {
+            continue;
+          }
+
+          /* Otherwise, some bad juju happened -- need to quit */
+
+          return LAM_ERR_IN_ERRNO;
+        }
+      } while (true);
+    }
+
+    /* Return the status to the caller */
+
+    return LAM_SUCCESS;
 }

src/lam/util/few.h

@@ -5,6 +5,6 @@
 #ifndef LAM_FEW_H
 #define LAM_FEW_H
 
-int lam_few (char *argv[]);
+int lam_few(char *argv[], int *status);
 
 #endif /* LAM_FEW_H */