Generate variable containing number of characters in a string variable

There is no egen function because there has long [sic] been a function strict sense to do this. In recent versions of Stata, the function is called strlen() but the older name length() continues to work:

. sysuse auto
(1978 Automobile Data)

. gen l1 = length(make)

. gen l2 = strlen(make)

. su l?

    Variable |        Obs        Mean    Std. Dev.       Min        Max
-------------+---------------------------------------------------------
          l1 |         74    11.77027    2.155257          6         17
          l2 |         74    11.77027    2.155257          6         17

See help functions and (e.g.) this tutorial column.