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memcached_auto

Incrementing and Decrementing Values

#include <libmemcached/memcached.h>
Compile and link with -lmemcached








  • ptr -- pointer to an initialized memcached_st <#_CPPv412memcached_st> struct
  • group_key -- key namespace
  • group_key_length -- length of the key namespace without any terminating zero
  • key -- the key
  • key_length -- length of the key without any terminating zero
  • offset -- offset to increment/decrement
  • initial -- initial value if key does not exist and expiration is not MEMCACHED_EXPIRATION_NOT_ADD
  • expiration -- expiration as a unix timestamp or as relative expiration time in seconds
  • value -- the resulting value after initialization/increment/decrement

memcached_return_t <#_CPPv418memcached_return_t> indicating success


memcached(1) <https://linux.die.net/man/1/memcached> servers have the ability to increment and decrement keys (overflow and underflow are not detected). This gives you the ability to use memcached to generate shared sequences of values.

memcached_increment() takes a key and key_length and increments the value by the offset passed to it. The value is then returned via the uint32_t value pointer you pass to it.

memcached_decrement() takes a key and key_length and decrements the value by the offset passed to it. The value is then returned via the uint32_t value pointer you pass to it.

memcached_increment_with_initial() takes a key and key_length and increments the value by the offset passed to it. If the object specified by key does not exist, one of two things may happen: If the expiration value is MEMCACHED_EXPIRATION_NOT_ADD <#c.MEMCACHED_EXPIRATION_NOT_ADD>, the operation will fail. For all other expiration values, the operation will succeed by seeding the value for that key with a initial value to expire with the provided expiration time. The flags will be set to zero. The value is then returned via the uint32_t value pointer you pass to it. memcached_increment_with_initial is only available when using the binary protocol.

memcached_decrement_with_initial() takes a key and key_length and decrements the value by the offset passed to it. If the object specified by key does not exist, one of two things may happen: If the expiration value is MEMCACHED_EXPIRATION_NOT_ADD <#c.MEMCACHED_EXPIRATION_NOT_ADD>, the operation will fail. For all other expiration values, the operation will succeed by seeding the value for that key with a initial value to expire with the provided expiration time. The flags will be set to zero. The value is then returned via the uint32_t value pointer you pass to it. memcached_decrement_with_initial() is only available when using the binary protocol.

memcached_increment_by_key(), memcached_decrement_by_key(), memcached_increment_with_initial_by_key(), and memcached_decrement_with_initial_by_key() are master key equivalents of the above.

A value of type memcached_return_t <#_CPPv418memcached_return_t> is returned. On success that value will be MEMCACHED_SUCCESS <#_CPPv4N18memcached_return_t17MEMCACHED_SUCCESSE>. Use memcached_strerror() <#_CPPv418memcached_strerrorP12memcached_st18memcached_return_t> to translate this value to a printable string.

memcached(1) <https://linux.die.net/man/1/memcached> libmemcached(3) <https://linux.die.net/man/3/libmemcached> memcached_strerror(3) <https://linux.die.net/man/3/memcached_strerror>