GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
Unix |
Unix v6 |
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exec(2) |
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exec, execl, execv execute a file (exec = 11.)
sys exec; name; args
name: <...\0>
args: arg0; arg1; ...; 0
arg0: <...\0>
arg1: <...\0>
... execl(name, arg0, arg1, ..., argn, 0)
char *name, *arg0, *arg1, ..., *argn; execv(name, argv)
char *name;
char *argv[ ]; overlays the calling process with the
named file, then transfers to the beginning of the core
image of the file. There can be no return from the file; the
calling core image is lost. Files remain open across calls.
Ignored signals remain ignored across but signals that are
caught are reset to their default values. Each user has a
user ID and group ID and an user ID and group ID. The real
ID identifies the person using the system; the effective ID
determines his access privileges. changes the effective user
and group ID to the owner of the executed file if the file
has the ‘‘set-user-ID’’ or
‘‘set-group-ID’’ modes. The real
user ID is not affected. The form of this call differs
somewhat depending on whether it is called from assembly
language or C; see below for the C version. The first
argument to is a pointer to the name of the file to be
executed. The second is the address of a null-terminated
list of pointers to arguments to be passed to the file.
Conventionally, the first argument is the name of the file.
Each pointer addresses a string terminated by a null byte.
Once the called file starts execution, the arguments are
available as follows. The stack pointer points to a word
containing the number of arguments. Just above this number
is a list of pointers to the argument strings. The arguments
are placed as high as possible in core.
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nargs |
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arg0 |
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... |
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argn |
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1 |
<arg0\0> |
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<argn\0> From C, two interfaces are available. is useful when a known file with known arguments is being called; the arguments to are the character strings constituting the file and the arguments; as in the basic call, the first argument is conventionally the same as the file name (or its last component). A 0 argument must end the argument list. The version is useful when the number of arguments is unknown in advance; the arguments to are the name of the file to be executed and a vector of strings containing the arguments. The last argument string must be followed by a 0 pointer. When a C program is executed, it is called as follows: |
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main(argc, argv) |
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int argc; |
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char **argv; where argc is the argument count and argv is an array of character pointers to the arguments themselves. As indicated, argc is conventionally at least one and the first member of the array points to a string containing the name of the file. is not directly usable in another since is 1 and not 0. fork (II) If the file cannot be found, if it is not executable, if it does not have a valid header (407, 410, or 411 octal as first word), if maximum memory is exceeded, or if the arguments require more than 512 bytes a return from constitutes the diagnostic; the error bit (c-bit) is set. Even for the super-user, at least one of the execute-permission bits must be set for a file to be executed. From C the returned value is 1. Only 512 characters of arguments are allowed. |
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exec(2) | |