diff --git a/bin/ps/ps.c b/bin/ps/ps.c
--- a/bin/ps/ps.c
+++ b/bin/ps/ps.c
@@ -147,16 +147,16 @@
 static void	 pidmax_init(void);
 static void	 usage(void);
 
-static char dfmt[] = "pid,tt,state,time,command";
-static char jfmt[] = "user,pid,ppid,pgid,sid,jobc,state,tt,time,command";
-static char lfmt[] = "uid,pid,ppid,cpu,pri,nice,vsz,rss,mwchan,state,"
-			"tt,time,command";
-static char   o1[] = "pid";
-static char   o2[] = "tt,state,time,command";
-static char ufmt[] = "user,pid,%cpu,%mem,vsz,rss,tt,state,start,time,command";
-static char vfmt[] = "pid,state,time,sl,re,pagein,vsz,rss,lim,tsiz,"
-			"%cpu,%mem,command";
-static char Zfmt[] = "label";
+static const char dfmt[] = "pid,tt,state,time,command";
+static const char jfmt[] = "user,pid,ppid,pgid,sid,jobc,state,tt,time,command";
+static const char lfmt[] = "uid,pid,ppid,cpu,pri,nice,vsz,rss,mwchan,state,"
+			   "tt,time,command";
+static const char   o1[] = "pid";
+static const char   o2[] = "tt,state,time,command";
+static const char ufmt[] = "user,pid,%cpu,%mem,vsz,rss,tt,state,start,time,command";
+static const char vfmt[] = "pid,state,time,sl,re,pagein,vsz,rss,lim,tsiz,"
+			   "%cpu,%mem,command";
+static const char Zfmt[] = "label";
 
 #define	PS_ARGS	"AaCcD:defG:gHhjJ:LlM:mN:O:o:p:rSTt:U:uvwXxZ"
 
@@ -316,7 +316,6 @@
 		case 'j':
 			parsefmt(jfmt, &varlist, 0);
 			_fmt = 1;
-			jfmt[0] = '\0';
 			break;
 		case 'L':
 			showkey();
@@ -324,7 +323,6 @@
 		case 'l':
 			parsefmt(lfmt, &varlist, 0);
 			_fmt = 1;
-			lfmt[0] = '\0';
 			break;
 		case 'M':
 			memf = optarg;
@@ -339,7 +337,6 @@
 			parsefmt(o1, &varlist, 1);
 			parsefmt(optarg, &varlist, 1);
 			parsefmt(o2, &varlist, 1);
-			o1[0] = o2[0] = '\0';
 			_fmt = 1;
 			break;
 		case 'o':
@@ -408,13 +405,11 @@
 			parsefmt(ufmt, &varlist, 0);
 			sortby = SORTCPU;
 			_fmt = 1;
-			ufmt[0] = '\0';
 			break;
 		case 'v':
 			parsefmt(vfmt, &varlist, 0);
 			sortby = SORTMEM;
 			_fmt = 1;
-			vfmt[0] = '\0';
 			break;
 		case 'w':
 			if (wflag)
@@ -442,7 +437,6 @@
 			break;
 		case 'Z':
 			parsefmt(Zfmt, &varlist, 0);
-			Zfmt[0] = '\0';
 			break;
 		case '?':
 		default: