WeeZer51402
Registered
how can flags be added to an executable, ex. ls -a
Flags with c
- Thread starter WeeZer51402
- Start date
binaryDigit
Registered
easiest way is to use argc and argv in your "main" function.
int main(int argc,char *argv[]);
where argc is a count of the number of parameters and argv is an array of pointers to the actual strings themselves. By default, argv[0] is the name of your application. So if you wrote a program named foo and it's main looked like this:
int main(int argc,char *argv[])
{
for (int i = 0;i <= argc;i++)
printf("argv[%d] == %s\n",i,argv);
}
If you execute
./foo abc 123
then your output should look like:
0 == foo
1 == abc
2 == 123
The only somewhat tricky thing to remember is the argv[0] thing, since your array will actually contain 1 more element than argc tells you (since 0 is always assumed). Also, the exact format of argv[0] varies between os's. Some give you just the executable, some give you a full path (e.g. /usr/bin/foo), some vary depending on exactly how it was launched:
./foo could give you 'foo' or '/usr/bin/foo' or './foo'
../bin/foo could give you 'foo', or '/usr/bin/foo' or '../bin/foo'.
etc
int main(int argc,char *argv[]);
where argc is a count of the number of parameters and argv is an array of pointers to the actual strings themselves. By default, argv[0] is the name of your application. So if you wrote a program named foo and it's main looked like this:
int main(int argc,char *argv[])
{
for (int i = 0;i <= argc;i++)
printf("argv[%d] == %s\n",i,argv);
}
If you execute
./foo abc 123
then your output should look like:
0 == foo
1 == abc
2 == 123
The only somewhat tricky thing to remember is the argv[0] thing, since your array will actually contain 1 more element than argc tells you (since 0 is always assumed). Also, the exact format of argv[0] varies between os's. Some give you just the executable, some give you a full path (e.g. /usr/bin/foo), some vary depending on exactly how it was launched:
./foo could give you 'foo' or '/usr/bin/foo' or './foo'
../bin/foo could give you 'foo', or '/usr/bin/foo' or '../bin/foo'.
etc
WeeZer51402
Registered
in traditional unix programs what is the signifigance of "-" in front of flags
binaryDigit
Registered
Just a convention used to more easily distinguish between flags vs values. Take "ls" as an example:
ls -l l
the line above does a long listing of files/dirs named 'l'. If you didn't have the - in front of the first l, you wouldn't be able to tell which was the flag and which the value.
You are free to use whatever you want, though convention says that you should use '-' to make your app more friendly.
WeeZer51402
Registered
ok, i got it, its moe for orgizational purposes than