I am actually surprised that postgres does not have a builtin function to deal with unix timestamps. After all it does run on linux which does use unix timestamps. So it must be a common problem. Here is a quick solution.

CREATE OR REPLACE FUNCTION parseunixtimestamp(int)
	RETURNS timestamp AS 
		'SELECT TIMESTAMP ''epoch'' + $1 * INTERVAL ''1 second'''
	LANGUAGE SQL;

Now you can use it in select or insert statements. Like this

INSERT INTO TABLE (name, createdon) VALUES("a value", parseunixtimestamp(55436437))

If you need to you can remove it again later by running

DROP FUNCTION parseunixtimestamp(integer);

A short code example to show how to overwrite the contents of argv. It is useful for when a password is passed on the command line and it should not be visible in the process list to other users on the same machine.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char **argv) {
	int i = 0;
	int len = 0;

	if (argc < 2) {
		printf("Usage: %s <some argument>\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	len = strlen(argv[1]);
	for(i=0;i<len;i++) {
		argv[1][i] = 'x';
	}

	system("ps f");

	return 0;
}

A short example of doing an inplace string reverse in C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void swap(char *a, char *b) {
    char tmp = *a;
    *a = *b;
    *b = tmp;
}


int main(int argc, char **argv) {
    if (argc < 2) {
        printf("Usage: %s <string>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    char *tmp = strdup(argv[1]);
    int len = strlen(tmp);
    int i = 0;

    for(i=0;i<len/2;i++) {
        swap(&tmp[i], &tmp[len - i - 1]);
    }

    printf("%s\n", tmp);

    free(tmp);
    return EXIT_SUCCESS;
}

I started using postgres and inside my first week I amnaged to find an issue with pg_relation_size. The problem being is that SQL is mean to be non case sensitive. So I guess this is a bug since if you have an table name with an upper case character in it things seem to break, Badly.

to put this in context I create a table called "Attempts". It is for analyzing password attempts from a honeypot. I wrote a quick syslog parser and fired the output into sql so I could run some quries. So I have the following in postgres.

=# \d
                 List of relations
 Schema |          Name          |   Type   | Owner
--------+------------------------+----------+-------
 public | Attempts               | table    | root
 public | Attempts_AttemptID_seq | sequence | root
(2 rows)

So that is really simple. The following works without a problem. This will also work with a lower case "attempts"

=# select count(*) from "Attempts";
 count
-------
 24490
(1 row)

The following however does not.

select pg_relation_size('Attempts');

ERROR:  relation "attempts" does not exist
LINE 1: select pg_relation_size('Attempts');

Neither does

select pg_relation_size('attempts');
ERROR:  relation "attempts" does not exist
LINE 1: select pg_relation_size('attempts');

Or this.

select pg_relation_size("attempts");
ERROR:  column "attempts" does not exist
LINE 1: select pg_relation_size("attempts");


select pg_relation_size("Attempts");
ERROR:  column "Attempts" does not exist
LINE 1: select pg_relation_size("Attempts");

Or this.

select tablename from pg_tables where tablename = 'Attempts';
 tablename
-----------
 Attempts
(1 row)


select tablename,  pg_relation_size(tablename) from pg_tables where tablename = 'attempts';
ERROR:  function pg_relation_size(name) does not exist
LINE 1: select tablename,  pg_relation_size(tablename) from pg_table...
                           ^

This does ...

create table tmp (id int);

select pg_relation_size('tmp');
 pg_relation_size
------------------
                0
(1 row)

However this does work for both cases.

ALTER TABLE "Attempts" RENAME TO "attempts"


select pg_relation_size('Attempts');
 pg_relation_size
------------------
          2080768
(1 row)



select pg_relation_size('attempts');
 pg_relation_size
------------------
          2080768
(1 row)

So I guess that is broken then! This becomes a real pain now. Since I am using some orm software and the schema is defined by the classes in the code and not the other way around. I guess there is an extrac tolower somewhere.

The following example will check for a palindrom in C. You know one of thoose words spelt the same forwards as backwards. The smart part of this program is the edge case where you have an odd number of letters in the string. Well actually this can simply be ignored since there is no point in comparing the middle charecter to its self.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int try(char *str) {
    int len = strlen(str);
    int i;
    for(i =0;i<len/2;i++)
        if (str[i] != str[len - 1 - i])
            return 0;
    return 1;
}

int main(int argc, char**argv) {
    char *s1 = "ffoof";
    char *s2 = "foof";
    char *s3 = "fooof";

    if (try(s1))
        printf("%s\n", s1);

    if (try(s2))
        printf("%s\n", s2);

    if (try(s3))
        printf("%s\n", s3);

    return 0;
}