Unix systems provide a family of functions that replace
the execution context of a process with a new context described by an
executable file. The names of these functions start with the prefix
exec, followed by one or two letters;
therefore, a generic function in the family is usually referred to as an
exec functions are listed
in Table 20-7; they
differ in how the parameters are interpreted.
Table 20-7. The exec functions
The first parameter of each function denotes the pathname of the
file to be executed. The pathname can be absolute or relative to the
process's current directory. Moreover, if the name does not include any
/ characters, the
execlp( ) and
execvp( ) functions search for the
executable file in all directories specified by the
PATH environment variable.
Besides the first parameter, the
execlp( ), and
execle( ) functions include a variable number
of additional parameters. Each points to a string describing a
command-line argument for the new program; as the "
l" character in the function names suggests,
the parameters are organized in a list terminated by a
NULL value. Usually, the first command-line
argument duplicates the executable filename. Conversely, the
execve( ) functions ...