在安装mpfr时出现以下错误：
-bash: ./mpfr-3.1.2/make: No such file or directory

[root@localhost opt]# ./mpfr-3.1.2/make
-bash: ./mpfr-3.1.2/make: No such file or directory
[root@localhost opt]# /opt/mpfr-3.1.2/make
-bash: /opt/mpfr-3.1.2/make: No such file or directory
[root@localhost opt]# ../mpfr-3.1.2/make
-bash: ../mpfr-3.1.2/make: No such file or directory
[root@localhost opt]# mpfr-3.1.2/make
-bash: mpfr-3.1.2/make: No such file or directory
[root@localhost opt]# mpfr-3.1.2/configure
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... /bin/mkdir -p
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
configure: error: source directory already configured; run "make distclean" there first
[root@localhost opt]# ./mpfr-3.1.2/configure
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... /bin/mkdir -p
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
configure: error: source directory already configured; run "make distclean" there first
[root@localhost opt]# 

注意：
configure可 以像下面这样执行：
mpfr-3.1.2/configure
或：
./mpfr-3.1.2/configure

但是make和make install 就不能像下面这样执行：
mpfr-3.1.2/make
或：
./mpfr-3.1.2/make

mpfr-3.1.2/make install
或：
./mpfr-3.1.2/make install