curl was first released in 1996.[9] It was originally named httpget and then became urlget before adopting the current name of curl[10][11] The original author and lead developer is the Swedish developer Daniel Stenberg, who created curl because he wanted to automate the fetching of currency exchange rates for IRC users.[2]
The libcurl library is portable. It builds and works identically on many platforms, including AIX, AmigaOS, Android,[citation needed] BeOS, BlackBerry Tablet OS and BlackBerry 10,[15] OpenVMS, Darwin, DOS, FreeBSD, HP-UX, HURD, iOS, IRIX, Linux, macOS, NetBSD, NetWare, OpenBSD, OS/2, QNX Neutrino, RISC OS, Solaris, Symbian, Tru64, Ultrix, UnixWare, and Microsoft Windows.[16]
The libcurl library supports GnuTLS, mbed TLS, NSS, gskit on IBM i, SChannel on Windows, Secure Transport on macOS and iOS, SSL/TLS through OpenSSL, BoringSSL, libreSSL, AmiSSL, wolfSSL, BearSSL and rustls.[18]
curl will return an error message if the remote server is using a self-signed certificate, or if the remote server certificate is not signed by a CA listed in the CA cert file. -k or --insecure option can be used to skip certificate verification. Alternatively, if the remote server is trusted, the remote server CA certificate can be added to the CA certificate store file.
curl defaults to displaying the output it retrieves to the standard output specified on the system (usually the terminal window). So running the command above would, on most systems, display the www.example.com source-code in the terminal window. The -o flag can be used to store the output in a file instead:
In vector calculus, the curl, also known as rotor, is a vector operator that describes the infinitesimal circulation of a vector field in three-dimensional Euclidean space. The curl at a point in the field is represented by a vector whose length and direction denote the magnitude and axis of the maximum circulation.[1] The curl of a field is formally defined as the circulation density at each point of the field.
A vector field whose curl is zero is called irrotational. The curl is a form of differentiation for vector fields. The corresponding form of the fundamental theorem of calculus is Stokes' theorem, which relates the surface integral of the curl of a vector field to the line integral of the vector field around the boundary curve.
One way to define the curl of a vector field at a point is implicitly through its projections onto various axes passing through the point: if u ^ \displaystyle \mathbf \hat u is any unit vector, the projection of the curl of F onto u ^ \displaystyle \mathbf \hat u may be defined to be the limiting value of a closed line integral in a plane orthogonal to u ^ \displaystyle \mathbf \hat u divided by the area enclosed, as the path of integration is contracted indefinitely around the point.
The above formula means that the projection of the curl of a vector field along a certain axis is the infinitesimal area density of the circulation of the field projected onto a plane perpendicular to that axis. This formula does not a priori define a legitimate vector field, for the individual circulation densities with respect to various axes a priori need not relate to each other in the same way as the components of a vector do; that they do indeed relate to each other in this precise manner must be proven separately.
Another way one can define the curl vector of a function F at a point is explicitly as the limiting value of a vector-valued surface integral around a shell enclosing p divided by the volume enclosed, as the shell is contracted indefinitely around p.
In this formula, the cross product in the integrand measures the tangential component of F at each point on the surface S, together with the orientation of these tangential components with respect to the surface S. Thus, the surface integral measures the overall extent to which F circulates around S, together with the net orientation of this circulation in space. The curl of a vector field at a point is then the infinitesimal volume density of the net vector circulation (i.e., both magnitude and spatial orientation) of the field around the point.
To this definition fits naturally another global formula (similar to the Kelvin-Stokes theorem) which equates the volume integral of the curl of a vector field to the above surface integral taken over the boundary of the volume.
In practice, the two coordinate-free definitions described above are rarely used because in virtually all cases, the curl operator can be applied using some set of curvilinear coordinates, for which simpler representations have been derived.
Suppose the vector field describes the velocity field of a fluid flow (such as a large tank of liquid or gas) and a small ball is located within the fluid or gas (the center of the ball being fixed at a certain point). If the ball has a rough surface, the fluid flowing past it will make it rotate. The rotation axis (oriented according to the right hand rule) points in the direction of the curl of the field at the center of the ball, and the angular speed of the rotation is half the magnitude of the curl at this point.[9]The curl of the vector field at any point is given by the rotation of an infinitesimal area in the xy-plane (for z-axis component of the curl), zx-plane (for y-axis component of the curl) and yz-plane (for x-axis component of the curl vector). This can be seen in the examples below.
The resulting vector field describing the curl would at all points be pointing in the negative z direction. The results of this equation align with what could have been predicted using the right-hand rule using a right-handed coordinate system. Being a uniform vector field, the object described before would have the same rotational intensity regardless of where it was placed.
The curl points in the negative z direction when x is positive and vice versa. In this field, the intensity of rotation would be greater as the object moves away from the plane x = 0.
The vector calculus operations of grad, curl, and div are most easily generalized in the context of differential forms, which involves a number of steps. In short, they correspond to the derivatives of 0-forms, 1-forms, and 2-forms, respectively. The geometric interpretation of curl as rotation corresponds to identifying bivectors (2-vectors) in 3 dimensions with the special orthogonal Lie algebra s o ( 3 ) \displaystyle \mathfrak so(3) of infinitesimal rotations (in coordinates, skew-symmetric 3 3 matrices), while representing rotations by vectors corresponds to identifying 1-vectors (equivalently, 2-vectors) and s o ( 3 ) \displaystyle \mathfrak so(3) , these all being 3-dimensional spaces.
the 1-dimensional fibers correspond to scalar fields, and the 3-dimensional fibers to vector fields, as described below. Modulo suitable identifications, the three nontrivial occurrences of the exterior derivative correspond to grad, curl, and div.
The curl of a 3-dimensional vector field which only depends on 2 coordinates (say x and y) is simply a vertical vector field (in the z direction) whose magnitude is the curl of the 2-dimensional vector field, as in the examples on this page.
In the case where the divergence of a vector field V is zero, a vector field W exists such that V = curl(W).[citation needed] This is why the magnetic field, characterized by zero divergence, can be expressed as the curl of a magnetic vector potential.
While it is possible to use curl from Elixir directly, it seems like what you actually want to do, is to perform a remote HTTP request and read the results.
Instead of manually using curl, I suggest using a HTTP client library such as HTTPoison, which does much of the request/response parsing and error handling for you.
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400 error would be a general error on Stripes side. Maybe try postman or curl on your own machine to make it 100% work then try it on bubble? Using bubble directly without testing could work but it adds additional complexity to troubleshoot.
In association with the release of curl 8.4.0, we publish a security advisory and all the details for CVE-2023-38545. This problem is the worst security problem found in curl in a long time. We set it to severity HIGH.
In early 2020 I assigned myself an old long-standing curl issue: to convert the function that connects to a SOCKS5 proxy from a blocking call into a non-blocking state machine. This is for example much noticeable when an application performs a large amount of parallel transfers that all go over SOCKS5.
This boolean variable holds information about whether curl should resolve the host or just pass on the name to the proxy. This assignment is done at the top and thus for every invocation while the state machine is running.
curl builds a protocol frame in a memory buffer, and it copies the destination to that buffer. Since the code wrongly thinks it should pass on the host name, even though the host name is too long to fit, the memory copy can overflow the allocated target buffer. Of course depending on the length of the host name and the size of the target buffer.
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