simple error check

2 files changed, 32 insertions, 3 deletions

diff --git a/tsh.cc b/tsh.cc
index 6800e4d..ebf4d6a 100644
--- a/tsh.cc
+++ b/tsh.cc
@@ -19,6 +19,7 @@
 
 using namespace std;
 using ov4::atomic_print;
+using ov4::isnum;
 
 /* Misc manifest constants */
 #define MAXLINE    1024   /* max line size */
@@ -339,11 +340,30 @@ void do_bgfg(char **argv)
         sigset_t prev;
         if (argv[1][0] == '%') // jid provided
         {
-            x = atoi(argv[1]); // eat %
+            if (!isnum(&argv[1][1]))
+            {
+                cerr << ((strcmp(argv[0], "fg") == 0) ? "fg" : "bg") << ": argument must be a PID or %jobid" << endl;
+                return;
+            }
+            x = atoi(&argv[1][1]); // eat %
             j = getjobjid(jobs, x);
+            if (j == nullptr)
+            {
+                cerr << argv[1] << ": No such job" << endl;
+            }
         } else { // pid
-            x = atoi(argv[0]);
+            if (!isnum(&argv[1][1]))
+            {
+                cerr << ((strcmp(argv[0], "fg") == 0) ? "fg" : "bg") << ": argument must be a PID or %jobid" << endl;
+                return;
+            }
+            x = atoi(&argv[1][0]);
             j = getjobpid(jobs, x);
+            if (j == nullptr)
+            {
+                cerr << argv[1] << ": No such process" << endl;
+                return;
+            }
         }
 
         block_all(&prev);
diff --git a/util.h b/util.h
index 072f65e..1477d3b 100644
--- a/util.h
+++ b/util.h
@@ -19,6 +19,7 @@ namespace ov4 {
 
 void atomic_print(char *s);
 void atomic_print(int x);
+bool isnum(char *s);
 void reverse(char str[], int length);
 char* itoa(int num, char* str, int base);
 
@@ -27,7 +28,7 @@ bool DEBUG = true; // verbose mode, can be enabled on demand using something lik
 struct LogVoidify { void operator&(std::ostream&) const {} };
 
 const int DECIMAL = 10;
-const int LENGTH = 20;
+const int LENGTH = 25;
 
 void atomic_print(char *s)
 {
@@ -54,6 +55,14 @@ void reverse(char str[], int length)
     }
 }
 
+bool isnum(char *s)
+{
+    for (int i = 0; s[i] != 0; i++)
+        if (!isdigit(s[i]))
+            return false;
+    return true;
+}
+
 
 char* itoa(int num, char* str, int base)
 {