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    <p>It is not always. It's the value that you gave the program by the Operation System. For example when starting a program using <code>exec</code> you can set that to an arbitrary value:</p> <pre><code>int execve(const char *filename, char *const argv[], char *const envp[]); </code></pre> <p>The first parameter is the file to start, and argv will contains argv[0] and all other parameters for main. envp contains the environment variables (not defined by Standard C or C++. This is a posix thing). </p> <p>More precisely, this is the definition of argv in C++:</p> <blockquote> <p>An implementation shall not predefine the main function. This function shall not be overloaded. It shall have a return type of type int, but otherwise its type is implementation-defined. All implementations shall allow both of the following definitions of main:</p> </blockquote> <pre><code>int main() { /* ... */ } </code></pre> <blockquote> <p>and</p> </blockquote> <pre><code>int main(int argc, char* argv[]) { /* ... */ } </code></pre> <blockquote> <p>In the latter form argc shall be the number of arguments passed to the program from the environment in which the program is run. If argc is nonzero these arguments shall be supplied in <code>argv[0]</code> through <code>argv[argc-1]</code> as pointers to the initial characters of null-terminated multibyte strings (NTMBSs) (17.3.2.1.3.2) and <code>argv[0]</code> shall be the pointer to the initial character of a NTMBS that represents the name used to invoke the program or "". The value of argc shall be nonnegative. The value of <code>argv[argc]</code> shall be 0. [Note: it is recommended that any further (optional) parameters be added after argv. ]</p> </blockquote> <p>It's pretty much up to the implementation what defines a "name used to invoke the program". If you want to get the full path of your executable, you can use <a href="http://msdn.microsoft.com/en-us/library/ms683197%28VS.85%29.aspx" rel="noreferrer">GetModuleFileName</a> on Windows, and <code>argv[0]</code> (for getting the name used to execute, may be relative) together with <code>getcwd</code> (for getting the current working directory, trying to make the name absolute).</p>
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    1. POIs args[0] guaranteed to be the path of execution?
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    1. USJohannes Schaub - litb
    1. USJohannes Schaub - litb
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    1. POIs args[0] guaranteed to be the path of execution?
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    1. COFor example, a shell knows it's a login shell because login(1) arranges for argv[0] to begin with a dash.
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      1. USNorman Ramsey
    2. CO... and bash knows it's in POSIX mode by comparing argv[0] to "sh" :) incidentally, this argv trickery is what makes busybox so small. all utils are packed together in one binary which is just executed with different argv[0] values
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      1. USJohannes Schaub - litb
    3. COI'd avoid realpath in portable programs. The POSIX realpath interface is broken, because you can't specify the size of the target buffer, nor allocate one big enough without making assumptions about PATH_MAX.
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