PostgreSQL数据库源码安装第一步——configure脚本分析（环境检测）

谁践踏了优雅 2022-11-05 08:48 162阅读 0赞

源码编译PG8.4.1时，需要在安装完几个依赖的开发库后，在源代码目录下运行configure脚本。下面我们就分析一下该名为configure的shell脚本。其主要功能是猜测系统依赖变量的值并创建Makefiles。

## 一、环境检测 ##

下面的代码是为了照顾zsh这种极品Shell，因为不使用zsh，所以这里不对代码进行分析。这里提一点emulate sh 到底是干什么的呢？Zsh can emulate sh, ksh, or csh. (csh is not fully emulated). zsh does an outstanding job in its sh and ksh emulation. You can start emulating another shell by running emulate some\_shell from the command line. If you add the -R flag, all options will be reset to their default values. You can also create a link called ‘csh’, or ‘ksh’, or ‘sh’ that points to zsh. Zsh will notice that it was invoked with a different name, and do its best to behave like the shell you specify.

# Be more Bourne compatible
    DUALCASE=1; export DUALCASE # for MKS sh
    if test -n "${ZSH_VERSION+set}" && (emulate sh) >/dev/null 2>&1; then
      emulate sh
      NULLCMD=:
      # Zsh 3.x and 4.x performs word splitting on ${1+"$@"}, which
      # is contrary to our usage. Disable this feature.
      alias -g '${1+"$@"}'='"$@"'
      setopt NO_GLOB_SUBST
    else
      case `(set -o) 2>/dev/null` in
      *posix*) set -o posix ;;
    esac
    fi

DUALCASE变量的解释如下[linux中特别的Shell变量 DUALCASE][linux_Shell_ DUALCASE]  
test –n 字符串 —> 判断字符串的长度非零  
set -o选项的解释[Linux中shell的 set命令 -e -o 选项作用][Linux_shell_ set_ -e -o]

PATH需要CR，避免依赖于Character Ranges，这里把所有字母和数字列出来。

1 as_cr_letters='abcdefghijklmnopqrstuvwxyz'
    2 as_cr_LETTERS='ABCDEFGHIJKLMNOPQRSTUVWXYZ'
    3 as_cr_Letters=$as_cr_letters$as_cr_LETTERS
    4 as_cr_digits='0123456789'
    5 as_cr_alnum=$as_cr_Letters$as_cr_digits

检测PATH\_SEPATATOR，即PATH变量的分隔符为;还是 。

# The user is always right.
    if test "${PATH_SEPARATOR+set}" != set; then
      echo "#! /bin/sh" >conf$$.sh
      echo  "exit 0"   >>conf$$.sh
      chmod +x conf$$.sh
      if (PATH="/nonexistent;."; conf$$.sh) >/dev/null 2>&1; then
        PATH_SEPARATOR=';'
      else
        PATH_SEPARATOR=:
      fi
      rm -f conf$$.sh
    fi

P A T H S E P A R A T O R + s e t 意 思 是 如 果 设 置 了 P A T H S E P A R A T O R , 则 用 s e t 置 换 变 量 ， 否 则 不 进 行 置 换 . 语 法 : ‘ 变 量 = \{PATH\_SEPARATOR+set\} 意思是如果设置了PATH\_SEPARATOR,则用set置换变量，否则不进行置换. 语法 :\`变量= PATHSEPARATOR\+set意思是如果设置了PATHSEPARATOR,则用set置换变量，否则不进行置换.语法:‘变量=\{参数+word\}\`:如果设置了参数,则用word置换变量,否则不进行置换.  
$$ 当前Shell进程ID。对于 Shell 脚本，就是这些脚本所在的进程ID。  
PATH="/nonexistent;." —> 暂时没明白什么意思

在可用的情况下，需要支持unset

1 if ( (MAIL=60; unset MAIL) || exit) >/dev/null 2>&1; then
    2   as_unset=unset
    3 else
    4   as_unset=false
    5 fi

需要空格，tab，新行以顺序排列，放置编辑器出现关于space-tab兼容性问题。如果调用\_AS\_PATH\_WALK时IFS没有设置，将会通过将IFS设置为空值，关闭word splitting。

1 as_nl=' 2 '
    3 IFS=" "" $as_nl"

查找出运行该脚本的用户

# Find who we are. Look in the path if we contain no directory separator.
    case $0 in
      *[\\/]* ) as_myself=$0 ;;
      *) as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
    for as_dir in $PATH
    do
      IFS=$as_save_IFS
      test -z "$as_dir" && as_dir=.
      test -r "$as_dir/$0" && as_myself=$as_dir/$0 && break
    done
    IFS=$as_save_IFS
    
         ;;
    esac

`$0`当前脚本的文件名

如果没有发现用户，可能是通过sh COMMAND运行的

if test "x$as_myself" = x; then
      as_myself=$0
    fi
    if test ! -f "$as_myself"; then
      echo "$as_myself: error: cannot find myself; rerun with an absolute file name" >&2
      {  (exit 1); exit 1; }
    fi

Work around bugs in pre-3.0 UWIN ksh.

for as_var in ENV MAIL MAILPATH
    do ($as_unset $as_var) >/dev/null 2>&1 && $as_unset $as_var
    done
    PS1='$ '
    PS2='> '
    PS4='+ '

NLS nuisances. 麻烦事 处理语言国际化，还原为默认设置

for as_var in \
      LANG LANGUAGE LC_ADDRESS LC_ALL LC_COLLATE LC_CTYPE LC_IDENTIFICATION \
      LC_MEASUREMENT LC_MESSAGES LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER \
      LC_TELEPHONE LC_TIME
    do
      if (set +x; test -z "`(eval $as_var=C; export $as_var) 2>&1`"); then
        eval $as_var=C; export $as_var
      else
        ($as_unset $as_var) >/dev/null 2>&1 && $as_unset $as_var
      fi
    done

basename 命令  
$ basename /usr/bin/sort 输出"sort"。  
$ basename ./include/stdio.h .h 输出"stdio"。  
为basename指定一个路径，basename命令会删掉所有的前缀包括最后一个slash（‘/’）字符，然后将字符串显示出来。  
basename命令格式:

basename [pathname] [suffix]
    basename [string] [suffix]

suffix为后缀，如果suffix被指定了，basename会将pathname或string中的suffix去掉。

# Required to use basename.
    if expr a : '$a$' >/dev/null 2>&1 &&
       test "X`expr 00001 : '.*$...$'`" = X001; then
      as_expr=expr
    else
      as_expr=false
    fi
    if (basename -- /) >/dev/null 2>&1 && test "X`basename -- / 2>&1`" = "X/"; then
      as_basename=basename
    else
      as_basename=false
    fi

可执行文件的名字

# Name of the executable.
    as_me=`$as_basename -- "$0" || $as_expr X/"$0" : '.*/$[^/][^/]*$/*$' \| \ X"$0" : 'X$//$$' \| \ X"$0" : 'X$/$' \| . 2>/dev/null || echo X/"$0" | sed '/^.*\/$[^/][^/]*$\/*$/{ s//\1/ q } /^X\/$\/\/$$/{ s//\1/ q } /^X\/$\/$.*/{ s//\1/ q } s/.*/./; q'`

对系统的命令的测试

if test "x$CONFIG_SHELL" = x; then
      if (eval ":") 2>/dev/null; then
      as_have_required=yes
    else
      as_have_required=no
    fi
    if test $as_have_required = yes &&      (eval ": (as_func_return () { (exit \$1) } as_func_success () { as_func_return 0 } as_func_failure () { as_func_return 1 } as_func_ret_success () { return 0 } as_func_ret_failure () { return 1 } exitcode=0 if as_func_success; then : else exitcode=1 echo as_func_success failed. fi if as_func_failure; then exitcode=1 echo as_func_failure succeeded. fi if as_func_ret_success; then : else exitcode=1 echo as_func_ret_success failed. fi if as_func_ret_failure; then exitcode=1 echo as_func_ret_failure succeeded. fi if ( set x; as_func_ret_success y && test x = \"\$1\" ); then : else exitcode=1 echo positional parameters were not saved. fi test \$exitcode = 0) || { (exit 1); exit 1; } ( as_lineno_1=\$LINENO as_lineno_2=\$LINENO test \"x\$as_lineno_1\" != \"x\$as_lineno_2\" && test \"x\`expr \$as_lineno_1 + 1\`\" = \"x\$as_lineno_2\") || { (exit 1); exit 1; } ") 2> /dev/null; then
    else
      as_candidate_shells=
        as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
    for as_dir in /bin$PATH_SEPARATOR/usr/bin$PATH_SEPARATOR$PATH
    do
      IFS=$as_save_IFS
      test -z "$as_dir" && as_dir=.
      case $as_dir in
         /*)
           for as_base in sh bash ksh sh5; do
             as_candidate_shells="$as_candidate_shells $as_dir/$as_base"
           done;;
           esac
    done
    IFS=$as_save_IFS
    
    
          for as_shell in $as_candidate_shells $SHELL; do
         # Try only shells that exist, to save several forks.
         if {  test -f "$as_shell" || test -f "$as_shell.exe"; } &&
            {  ("$as_shell") 2> /dev/null <<\_ASEOF
    if test -n "${ZSH_VERSION+set}" && (emulate sh) >/dev/null 2>&1; then
      emulate sh
      NULLCMD=:
      # Zsh 3.x and 4.x performs word splitting on ${1+"$@"}, which
      # is contrary to our usage. Disable this feature.
      alias -g '${1+"$@"}'='"$@"'
      setopt NO_GLOB_SUBST
    else
      case `(set -o) 2>/dev/null` in
      *posix*) set -o posix ;;
    esac
    
    fi
    
    
    :
    _ASEOF
    }; then
      CONFIG_SHELL=$as_shell
    	       as_have_required=yes
    	       if {  "$as_shell" 2> /dev/null <<\_ASEOF
    if test -n "${ZSH_VERSION+set}" && (emulate sh) >/dev/null 2>&1; then
      emulate sh
      NULLCMD=:
      # Zsh 3.x and 4.x performs word splitting on ${1+"$@"}, which
      # is contrary to our usage. Disable this feature.
      alias -g '${1+"$@"}'='"$@"'
      setopt NO_GLOB_SUBST
    else
      case `(set -o) 2>/dev/null` in
      *posix*) set -o posix ;;
    esac
    
    fi
    
    
    :
    (as_func_return () { 
      (exit $1)
    }
    as_func_success () { 
      as_func_return 0
    }
    as_func_failure () { 
      as_func_return 1
    }
    as_func_ret_success () { 
      return 0
    }
    as_func_ret_failure () { 
      return 1
    }
    
    exitcode=0
    if as_func_success; then
      :
    else
      exitcode=1
      echo as_func_success failed.
    fi
    
    if as_func_failure; then
      exitcode=1
      echo as_func_failure succeeded.
    fi
    
    if as_func_ret_success; then
      :
    else
      exitcode=1
      echo as_func_ret_success failed.
    fi
    
    if as_func_ret_failure; then
      exitcode=1
      echo as_func_ret_failure succeeded.
    fi
    
    if ( set x; as_func_ret_success y && test x = "$1" ); then
      :
    else
      exitcode=1
      echo positional parameters were not saved.
    fi
    
    test $exitcode = 0) || {  (exit 1); exit 1; }
    
    (
      as_lineno_1=$LINENO
      as_lineno_2=$LINENO
      test "x$as_lineno_1" != "x$as_lineno_2" &&
      test "x`expr $as_lineno_1 + 1`" = "x$as_lineno_2") || {  (exit 1); exit 1; }
    
    _ASEOF
    }; then
      break
    fi
    
    fi
    
          done
    
          if test "x$CONFIG_SHELL" != x; then
      for as_var in BASH_ENV ENV
            do ($as_unset $as_var) >/dev/null 2>&1 && $as_unset $as_var
            done
            export CONFIG_SHELL
            exec "$CONFIG_SHELL" "$as_myself" ${ 1+"$@"}
    fi
    
    
        if test $as_have_required = no; then
      echo This script requires a shell more modern than all the
          echo shells that I found on your system.  Please install a
          echo modern shell, or manually run the script under such a
          echo shell if you do have one.
          {  (exit 1); exit 1; }
    fi
    
    
    fi
    
    fi
    
    
    
    (eval "as_func_return () { (exit \$1) } as_func_success () { as_func_return 0 } as_func_failure () { as_func_return 1 } as_func_ret_success () { return 0 } as_func_ret_failure () { return 1 } exitcode=0 if as_func_success; then : else exitcode=1 echo as_func_success failed. fi if as_func_failure; then exitcode=1 echo as_func_failure succeeded. fi if as_func_ret_success; then : else exitcode=1 echo as_func_ret_success failed. fi if as_func_ret_failure; then exitcode=1 echo as_func_ret_failure succeeded. fi if ( set x; as_func_ret_success y && test x = \"\$1\" ); then : else exitcode=1 echo positional parameters were not saved. fi test \$exitcode = 0") || { 
      echo No shell found that supports shell functions.
      echo Please tell autoconf@gnu.org about your system,
      echo including any error possibly output before this
      echo message
    }

[linux_Shell_ DUALCASE]: https://feishujun.blog.csdn.net/article/details/114790818
[Linux_shell_ set_ -e -o]: https://feishujun.blog.csdn.net/article/details/114792111