Copyright (C) 1994, 1995, 1996, 1999, 2000, 2001, 2002, 2004, 2005 Free Software Foundation, Inc.

This file is free documentation; the Free Software Foundation gives unlimited permission to copy, distribute and modify it.

SPDX-License-Identifier: FSFULLR

If you want to build directly from the git repository, you must first generate the configure script and Makefile using autotools. Make sure that autoconf, automake and libtool are installed on your system, then execute:

autoreconf -fi

After executing this script, you can build the project as usual:

./configure
make

These are generic installation instructions.

The configure shell script attempts to guess correct values for various system-dependent variables used during compilation. It uses those values to create a Makefile in each directory of the package. It may also create one or more .h files containing system-dependent definitions. Finally, it creates a shell script config.status that you can run in the future to recreate the current configuration, and a file config.log containing compiler output (useful mainly for debugging configure).

It can also use an optional file (typically called config.cache and enabled with --cache-file=config.cache or shortly -C) that saves the results of its tests to speed up reconfiguring. (Caching is disabled by default to prevent problems with accidental use of stale cache files.)

If you need to do unusual things to compile the package, please try to figure out how configure could check whether to do them, and mail diffs or instructions to the address given in the README so they can be considered for the next release. If you are using the cache, and at some point config.cache contains results you do not want to keep, you may remove or edit it.

The file configure.ac (or configure.in) is used to create configure by a program called autoconf. You only need configure.ac if you want to change it or regenerate configure using a newer version of autoconf.

The simplest way to compile this package is:

1. cd to the directory containing the package's source code and type ./configure to configure the package for your system. If you are using csh on an old version of System V, you might need to type sh ./configure instead to prevent csh from trying to execute configure itself.

   Running configure takes awhile. While running, it prints some messages telling which features it is checking for.

2. Type make to compile the package.

3. Optionally, type make check to run any self-tests that come with the package.

4. Type make install to install the programs and any data files and documentation.

5. You can remove the program binaries and object files from the source code directory by typing make clean. To also remove the files that configure created (so you can compile the package for a different kind of computer), type make distclean. There is also a make maintainer-clean target, but that is intended mainly for the package's developers. If you use it, you may have to get all sorts of other programs in order to regenerate files that came with the distribution.

Some systems require unusual options for compilation or linking that the configure script does not know about. Run ./configure --help for details on some of the pertinent environment variables.

You can give configure initial values for configuration parameters by setting variables in the command line or in the environment. Here is an example:

./configure CC=c89 CFLAGS=-O2 LIBS=-lposix

*Note Defining Variables::, for more details.

You can compile the package for more than one kind of computer at the same time, by placing the object files for each architecture in their own directory. To do this, you must use a version of make that supports the VPATH variable, such as GNU make. cd to the directory where you want the object files and executables to go and run the configure script. configure automatically checks for the source code in the directory that configure is in and in ...

If you have to use a make that does not support the VPATH variable, you have to compile the package for one architecture at a time in the source code directory. After you have installed the package for one architecture, use make distclean before reconfiguring for another architecture.

By default, make install installs the package's commands under /usr/local/bin, include files under /usr/local/include, etc. You can specify an installation prefix other than /usr/local by giving configure the option --prefix=PREFIX.

You can specify separate installation prefixes for architecture-specific files and architecture-independent files. If you pass the option --exec-prefix=PREFIX to configure, the package uses PREFIX as the prefix for installing programs and libraries. Documentation and other data files still use the regular prefix.

In addition, if you use an unusual directory layout you can give options like --bindir=DIR to specify different values for particular kinds of files. Run configure --help for a list of the directories you can set and what kinds of files go in them.

If the package supports it, you can cause programs to be installed with an extra prefix or suffix on their names by giving configure the option --program-prefix=PREFIX or --program-suffix=SUFFIX.

Some packages pay attention to --enable-FEATURE options to configure, where FEATURE indicates an optional part of the package. They may also pay attention to --with-PACKAGE options, where PACKAGE is something like gnu-as or x (for the X Window System). The README should mention any --enable- and --with- options that the package recognizes.

For packages that use the X Window System, configure can usually find the X include and library files automatically, but if it does not, you can use the configure options --x-includes=DIR and --x-libraries=DIR to specify their locations.

There may be some features configure cannot figure out automatically, but needs to determine by the type of machine the package will run on. Usually, assuming the package is built to be run on the same architectures, configure can figure that out, but if it prints a message saying it cannot guess the machine type, give it the --build=TYPE option. TYPE can either be a short name for the system type, such as sun4, or a canonical name which has the form:

CPU-COMPANY-SYSTEM

where SYSTEM can have one of these forms:

OS KERNEL-OS

See the file config.sub for the possible values of each field. If config.sub is not included in this package, then this package does not need to know the machine type.

If you are building compiler tools for cross-compiling, you should use the option --target=TYPE to select the type of system they will produce code for.

If you want to use a cross compiler, that generates code for a platform different from the build platform, you should specify the "host" platform (i.e., that on which the generated programs will eventually be run) with --host=TYPE.

If you want to set default values for configure scripts to share, you can create a site shell script called config.site that gives default values for variables like CC, cache_file, and prefix. configure looks for PREFIX/share/config.site if it exists, then PREFIX/etc/config.site if it exists. Or, you can set the CONFIG_SITE environment variable to the location of the site script. A warning: not all configure scripts look for a site script.

Variables not defined in a site shell script can be set in the environment passed to configure. However, some packages may run configure again during the build, and the customized values of these variables may be lost. In order to avoid this problem, you should set them in the configure command line, using VAR=value. For example:

./configure CC=/usr/local2/bin/gcc

causes the specified gcc to be used as the C compiler (unless it is overridden in the site shell script). Here is a another example:

/bin/bash ./configure CONFIG_SHELL=/bin/bash

Here the CONFIG_SHELL=/bin/bash operand causes subsequent configuration-related scripts to be executed by /bin/bash.

configure recognizes the following options to control how it operates.

• --help, -h

  Print a summary of the options to configure, and exit.

• --version, -V

  Print the version of Autoconf used to generate the configure script, and exit.

• --cache-file=FILE

  Enable the cache: use and save the results of the tests in FILE, traditionally config.cache. FILE defaults to /dev/null to disable caching.

• --config-cache, -C

  Alias for --cache-file=config.cache.

• --quiet, --silent, -q

  Do not print messages saying which checks are being made. To suppress all normal output, redirect it to /dev/null (any error messages will still be shown).

• --srcdir=DIR

  Look for the package's source code in directory DIR. Usually configure can determine that directory automatically.

configure also accepts some other, not widely useful, options. Run configure --help for more details.

Some ./configure options deserve additional comments:

• --with-libgcrypt

• --without-libgcrypt

• --with-libgcrypt-prefix=DIR

  libssh2 can use the Libgcrypt library for cryptographic operations. One of the cryptographic libraries is required.

  Configure will attempt to locate Libgcrypt automatically.

  If your installation of Libgcrypt is in another location, specify it using --with-libgcrypt-prefix.

• --with-openssl

• --without-openssl

• --with-libssl-prefix=[DIR]

  libssh2 can use the OpenSSL library for cryptographic operations. One of the cryptographic libraries is required.

  Configure will attempt to locate OpenSSL in the default location.

  If your installation of OpenSSL is in another location, specify it using --with-libssl-prefix.

• --with-mbedtls

• --without-mbedtls

• --with-libmbedcrypto-prefix=[DIR]

  libssh2 can use the mbedTLS library for cryptographic operations. One of the cryptographic libraries is required.

  Configure will attempt to locate mbedTLS in the default location.

  If your installation of mbedTLS is in another location, specify it using --with-libmbedcrypto-prefix.

• --with-libz

• --without-libz

• --with-libz-prefix=[DIR]

  If present, libssh2 will attempt to use the zlib for payload compression, however zlib is not required.

  If your installation of Libz is in another location, specify it using --with-libz-prefix.

• --enable-debug

  Will make the build use more pedantic and strict compiler options as well as enable the libssh2_trace() function (for showing debug traces).