Print error if exit code is not 127

preview.c

@@ -5,6 +5,8 @@
 #include "error.h"
 #include "preview.h"
 
+#define FAILED_PREVIEW_EC 127
+
 #define PREVP_SIZE sizeof(Preview *)
 
 static char shell[] = "sh";
@@ -111,13 +113,37 @@ static void check_init_previews(void)
     }
 }
 
+#define CMD_ERR_BUF 256
+
 static int run(Preview *p, int *exitcode)
 {
+    int pipe_fd[2];
+    ERRCHK_RET(pipe(pipe_fd) == -1, FUNCFAILED("pipe"), ERRNOS);
+
+    int fd = STDERR_FILENO;
+    int *sp_arg[] = { pipe_fd, &fd };
+
     char *args[] = { shell, "-c", p->script, shell, NULL };
+    int ret = spawn(args, NULL, exitcode, spawn_redirect, sp_arg);
 
-    int *fds[] = { (int[]){ STDOUT_FILENO, STDERR_FILENO }, NULL };
+    close(pipe_fd[1]);
 
-    return spawn(args, NULL, exitcode, fds);
+    if (*exitcode != FAILED_PREVIEW_EC) {
+        char buf[CMD_ERR_BUF];
+        int len;
+        while ((len = read(pipe_fd[0], buf, CMD_ERR_BUF)) > 0) {
+            write(STDOUT_FILENO, buf, len);
+        }
+
+        if (len == -1) {
+            PRINTINTERR(FUNCFAILED("read"), ERRNOS);
+            ret = ERR;
+        }
+    }
+
+    close(pipe_fd[0]);
+
+    return ret;
 }
 
 #define SET_PENV(n, v)                                                 \
@@ -152,7 +178,7 @@ run:
     }
 
     ERRCHK_RET_OK(run(p, &exitcode));
-    if (exitcode == 127) {
+    if (exitcode == FAILED_PREVIEW_EC) {
         i++;
         goto run;
     }

utils.c

@@ -8,16 +8,28 @@
 
 char *program;
 
+int spawn_redirect(const void *arg)
+{
+    int **fds = (int **)arg;
+    int *pipe = fds[0];
+    int *fd = fds[1];
+
+    ERRCHK_RET(close(pipe[0]) == -1, FUNCFAILED("close"), ERRNOS);
+    ERRCHK_RET(dup2(pipe[1], *fd) == -1, FUNCFAILED("dup2"), ERRNOS);
+
+    return OK;
+}
+
 /*
  * Call command
  *
  * If cpid is NULL, wait for the command to finish executing;
  * otherwise store pid in cpid
  *
- * fd is a NULL-terminated array of pairs of file descriptors
+ * cfunc is a function to call when child process is created
- * to pass to dup2()
  */
-int spawn(char *args[], pid_t *cpid, int *exitcode, int *fds[2])
+int spawn(char *args[], pid_t *cpid, int *exitcode, int (*cfunc)(const void *),
+          const void *carg)
 {
     if (exitcode)
         *exitcode = -1;
@@ -27,15 +39,8 @@ int spawn(char *args[], pid_t *cpid, int *exitcode, int *fds[2])
 
     /* Child process */
     if (pid == 0) {
-        if (fds) {
+        if (cfunc && (cfunc(carg) != OK))
-            while (*fds) {
-                if (dup2((*fds)[0], (*fds)[1]) == -1) {
-                    print_errorf("dup2() failed: %s", strerror(errno));
             exit(EXIT_FAILURE);
-                }
-                fds = &fds[1];
-            }
-        }
 
         execvp(args[0], args);
         PRINTINTERR(FUNCFAILED("exec"), ERRNOS);

utils.h

@@ -26,7 +26,9 @@ typedef struct {
 
 extern char *program;
 
-int spawn(char *args[], pid_t *cpid, int *exitcode, int *fds[2]);
+int spawn_redirect(const void *arg);
+int spawn(char *args[], pid_t *cpid, int *exitcode, int (*cfunc)(const void *),
+          const void *carg);
 
 int strcmpnull(char const *s1, char const *s2);