From 1f9e8612be6409a4e1d49381849e426ac2153ae8 Mon Sep 17 00:00:00 2001
From: Kirill A. Korinskiy <catap@catap.ru>
Date: Thu, 18 Feb 2010 19:49:13 +0300
Subject: [PATCH] Implement support {x,y} syntax for take random number from range {x,y}
Cc: catap@catap.ru

---
 man/crontab.5 |    7 +++++++
 src/cron.c    |    1 +
 src/entry.c   |   37 ++++++++++++++++++++++++++++++++++++-
 3 files changed, 44 insertions(+), 1 deletions(-)

diff --git a/man/crontab.5 b/man/crontab.5
index 5942ef3..e6cf05e 100644
--- a/man/crontab.5
+++ b/man/crontab.5
@@ -186,6 +186,13 @@ field matches the current time.  For example,
 "30 4 1,15 * 5"
 would cause a command to be run at 4:30 am on the 1st and 15th of each
 month, plus every Friday.
+.PP
+You can use a random number from the range instead of any number. For
+example,
+.br
+"*/{4,6} * * *"
+run command every 4, 5 or 6 minutes. An integer random number is
+chosen from a range every time of loading file.
 .SH EXAMPLE CRON FILE                                                                                                         
 .nf                                                                                                                           
 # use /bin/sh to run commands, no matter what /etc/passwd says                                                                
diff --git a/src/cron.c b/src/cron.c
index 7b57932..bcc9c9b 100644
--- a/src/cron.c
+++ b/src/cron.c
@@ -221,6 +221,7 @@ int main(int argc, char *argv[]) {
 	}
 
 	pid = getpid();
+	srandom(pid);
 	acquire_daemonlock(0);
 	database.head = NULL;
 	database.tail = NULL;
diff --git a/src/entry.c b/src/entry.c
index 97cafc8..2b1adf2 100644
--- a/src/entry.c
+++ b/src/entry.c
@@ -49,6 +49,7 @@ static const char *ecodes[] = {
 
 static int get_list(bitstr_t *, int, int, const char *[], int, FILE *),
 get_range(bitstr_t *, int, int, const char *[], int, FILE *),
+get_num(int *, int, const char *[], int, FILE *, const char *),
 get_number(int *, int, const char *[], int, FILE *, const char *),
 set_element(bitstr_t *, int, int, int);
 
@@ -520,7 +521,7 @@ get_range(bitstr_t * bits, int low, int high, const char *names[],
 }
 
 static int
-get_number(int *numptr, int low, const char *names[], int ch, FILE * file,
+get_num(int *numptr, int low, const char *names[], int ch, FILE * file,
 	const char *terms) {
 	char temp[MAX_TEMPSTR], *pc;
 	int len, i;
@@ -570,6 +571,40 @@ get_number(int *numptr, int low, const char *names[], int ch, FILE * file,
 	return (EOF);
 }
 
+static int
+get_number(int *numptr, int low, const char *names[], int ch, FILE * file,
+	const char *terms) {
+	int num1, num2, rnd;
+
+	/* first look a start of random number */
+	if ((unsigned char) ch != '{') {
+		return get_num(numptr, low, names, ch, file, terms);
+	}
+
+	ch = get_char(file);
+
+	ch = get_number(&num1, 0, PPC_NULL, ch, file, ",");
+	if (ch == EOF)
+		return (EOF);
+
+	ch = get_char(file);
+
+	ch = get_number(&num2, 0, PPC_NULL, ch, file, "}");
+	if (ch == EOF)
+		return (EOF);
+
+	/* skip '}' */
+	ch = get_char(file);
+
+	rnd = random();
+
+	*numptr = num1 + (rnd / (RAND_MAX/(num2 - num1)));
+
+	Debug(DPARS | DEXT, ("get_number, {%d, %d} = %d\n", num1, num2, *numptr))
+
+	return ch;
+}
+
 static int set_element(bitstr_t * bits, int low, int high, int number) {
 	Debug(DPARS | DEXT, ("set_element(?,%d,%d,%d)\n", low, high, number))
 
-- 
1.6.6