shell脚本执行错误 $‘r‘:command not found

今天在Windows下编辑了一段CentOS7下编译安装ffmpeg源代码以及相关依赖软件包的编译sh脚本，直接拷贝到CentOS7下报错了：出现$’r’:command not found的错误。

在linux上执行脚本时出现$’r’:command not found,然而仔细检查脚本，对应行位置只是一个空行，并没有问题，那么linux为什么会将一个回车的空行报错？

原因是这样的：脚本是在window下编辑完成后上传到linux上执行的，win下的换行是回车符+换行符，也就是rn,而unix下是换行符n。linux下不识别r为回车符，所以导致每行的配置都多了个r，因此是脚本编码的问题。

在linux上执行 dos2unix 脚本名，再次执行脚本，报错消失。如果没有安装dos2unix这个命令，在CentOS中执行yum install dos2unix安装，如果是Ubuntu执行apt-get install dos2unix即可。

下面附上在CentOS7下编译安装ffmpeg以及相关依赖库的源代码的Shell脚本，参考了Compile FFmpeg on CentOS这篇文章，其中有些依赖库的下载地址已经失效，我换成了从http://www.linuxfromscratch.org/上面下载源代码。

# install required software package
#yum install autoconf automake bzip2 bzip2-devel cmake freetype-devel gcc gcc-c++ git libtool make mercurial pkgconfig zlib-devel

mkdir ~/ffmpeg_sources

INSTALL_PATH=/usr/local

# build and install nasm
# An assembler used by some libraries. Highly recommended or your resulting build may be very slow.
cd ~/ffmpeg_sources
curl -O -L https://www.nasm.us/pub/nasm/releasebuilds/2.14.02/nasm-2.14.02.tar.bz2
tar xjvf nasm-2.14.02.tar.bz2
cd nasm-2.14.02
./autogen.sh
./configure --prefix="$INSTALL_PATH" --bindir="$INSTALL_PATH/bin"
make
make install

# build and install Yasm
# An assembler used by some libraries. Highly recommended or your resulting build may be very slow.
cd ~/ffmpeg_sources
curl -O -L https://www.tortall.net/projects/yasm/releases/yasm-1.3.0.tar.gz
tar xzvf yasm-1.3.0.tar.gz
cd yasm-1.3.0
./configure --prefix="$INSTALL_PATH" --bindir="$INSTALL_PATH/bin"
make
make install


# build and install libx264
# H.264 video encoder. See the H.264 Encoding Guide for more information and usage examples.
# Requires ffmpeg to be configured with --enable-gpl --enable-libx264.
cd ~/ffmpeg_sources
git clone --depth 1 https://code.videolan.org/videolan/x264.git
curl -O -L http://anduin.linuxfromscratch.org/BLFS/x264/x264-20200819.tar.xz
xz -d x264-20200819.tar.xz
tar -xvf x264-20200819.tar
mv x264-20200819 x264
cd x264
PKG_CONFIG_PATH="$INSTALL_PATH/lib/pkgconfig" ./configure --prefix="$INSTALL_PATH" --bindir="$INSTALL_PATH/bin" --enable-static
make
make install

# build and install libx265
# H.265/HEVC video encoder. See the H.265 Encoding Guide for more information and usage examples.
# Requires ffmpeg to be configured with --enable-gpl --enable-libx265.
cd ~/ffmpeg_sources
# hg clone https://bitbucket.org/multicoreware/x265
curl -O -L http://anduin.linuxfromscratch.org/BLFS/x265/x265_3.4.tar.gz
tar -xzvf x265_3.4.tar.gz
mv x265_3.4 x265
cd ~/ffmpeg_sources/x265/build/linux
cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX="$INSTALL_PATH" -DENABLE_SHARED:bool=off ../../source
make
make install


# build and install libfdk_aac
# AAC audio encoder. See the AAC Audio Encoding Guide for more information and usage examples.
# Requires ffmpeg to be configured with --enable-libfdk_aac (and --enable-nonfree if you also included --enable-gpl).
cd ~/ffmpeg_sources
git clone --depth 1 https://github.com/mstorsjo/fdk-aac
cd fdk-aac
autoreconf -fiv
./configure --prefix="$INSTALL_PATH" --disable-shared
make
make install

# build and install libmp3lame
# MP3 audio encoder.
# Requires ffmpeg to be configured with --enable-libmp3lame.
cd ~/ffmpeg_sources
curl -O -L https://downloads.sourceforge.net/project/lame/lame/3.100/lame-3.100.tar.gz
tar xzvf lame-3.100.tar.gz
cd lame-3.100
./configure --prefix="$INSTALL_PATH" --bindir="$INSTALL_PATH/bin" --disable-shared --enable-nasm
make
make install

# build and install libopus
# Opus audio decoder and encoder.
# Requires ffmpeg to be configured with --enable-libopus.
cd ~/ffmpeg_sources
curl -O -L https://archive.mozilla.org/pub/opus/opus-1.3.1.tar.gz
tar xzvf opus-1.3.1.tar.gz
cd opus-1.3.1
./configure --prefix="$INSTALL_PATH" --disable-shared
make
make install

# libvpx
# VP8/VP9 video encoder and decoder. See the VP9 Video Encoding Guide for more information and usage examples.
# Requires ffmpeg to be configured with --enable-libvpx.
cd ~/ffmpeg_sources
# git clone --depth 1 https://chromium.googlesource.com/webm/libvpx.git
curl -O -L https://github.com/webmproject/libvpx/archive/v1.9.0/libvpx-1.9.0.tar.gz
tar xzvf libvpx-1.9.0.tar.gz
cd libvpx-1.9.0
./configure --prefix="$INSTALL_PATH" --disable-examples --disable-unit-tests --enable-vp9-highbitdepth --as=yasm
make
make install

# build and install FFmpeg
cd ~/ffmpeg_sources
curl -O -L https://ffmpeg.org/releases/ffmpeg-snapshot.tar.bz2
tar xjvf ffmpeg-snapshot.tar.bz2
cd ffmpeg
PATH="$INSTALL_PATH/bin:$PATH" PKG_CONFIG_PATH="$INSTALL_PATH/lib/pkgconfig" ./configure 
  --prefix="$INSTALL_PATH" 
  --pkg-config-flags="--static" 
  --extra-cflags="-I$INSTALL_PATH/include" 
  --extra-ldflags="-L$INSTALL_PATH/lib" 
  --extra-libs=-lpthread 
  --extra-libs=-lm 
  --bindir="$INSTALL_PATH/bin" 
  --enable-gpl 
  --enable-libfdk_aac 
  --enable-libfreetype 
  --enable-libmp3lame 
  --enable-libopus 
  --enable-libvpx 
  --enable-libx264 
  --enable-libx265 
  --enable-nonfree
make
make install
hash -d ffmpeg

注意：编译安装ffmpeg源代码要以root或者超级用户权限执行，并chmod +x build_ffmpeg_all.sh为脚本添加可执行权限运行： sh build_ffmpeg_all.sh