Linux shell编程学习笔记29：shell自带的 脚本调试 选项

Linux shell脚本的调试方法比较多，上次我们探讨和测试了shell内建命令set所提供的一些调试选项，其实 shell 本身也提供了一些调试选项。我们以bash为例来看看。

1 bash 的命令行帮助信息（bash --help）

purleEndurer @ csdn ~ $ bash --help
GNU bash, version 4.2.46(2)-release-(x86_64-redhat-linux-gnu)
Usage:  bash [GNU long option] [option] ...
        bash [GNU long option] [option] script-file ...
GNU long options:
        --debug
        --debugger
        --dump-po-strings
        --dump-strings
        --help
        --init-file
        --login
        --noediting
        --noprofile
        --norc
        --posix
        --protected
        --rcfile
        --rpm-requires
        --restricted
        --verbose
        --version
Shell options:
        -irsD or -c command or -O shopt_option          (invocation only)
        -abefhkmnptuvxBCHP or -o option
Type `bash -c "help set"' for more information about shell options.
Type `bash -c help' for more information about shell builtin commands.
purleEndurer @ csdn ~ $ 

 可以看到，bash命令有很多参数和选项。

使用 bash 命令加上特定的选项可以在运行Shell脚本时改变其行为，帮助我们诊断问题。

2  bash 的内置命令set提供的选项（bash -c "help set" ）

我们可以使用命令 bash -c "help set" 查看 bash 内置命令set提供的选项。

purpleEndurer @ cdu ~ $ bash -c "help set"
set: set [-abefhkmnptuvxBCHP] [-o option-name] [--] [arg ...]
    Set or unset values of shell options and positional parameters.
    
    Change the value of shell attributes and positional parameters, or
    display the names and values of shell variables.
    
    Options:
      -a  Mark variables which are modified or created for export.
      -b  Notify of job termination immediately.
      -e  Exit immediately if a command exits with a non-zero status.
      -f  Disable file name generation (globbing).
      -h  Remember the location of commands as they are looked up.
      -k  All assignment arguments are placed in the environment for a
          command, not just those that precede the command name.
      -m  Job control is enabled.
      -n  Read commands but do not execute them.
      -o option-name
          Set the variable corresponding to option-name:
              allexport    same as -a
              braceexpand  same as -B
              emacs        use an emacs-style line editing interface
              errexit      same as -e
              errtrace     same as -E
              functrace    same as -T
              hashall      same as -h
              histexpand   same as -H
              history      enable command history
              ignoreeof    the shell will not exit upon reading EOF
              interactive-comments
                           allow comments to appear in interactive commands
              keyword      same as -k
              monitor      same as -m
              noclobber    same as -C
              noexec       same as -n
              noglob       same as -f
              nolog        currently accepted but ignored
              notify       same as -b
              nounset      same as -u
              onecmd       same as -t
              physical     same as -P
              pipefail     the return value of a pipeline is the status of
                           the last command to exit with a non-zero status,
                           or zero if no command exited with a non-zero status
              posix        change the behavior of bash where the default
                           operation differs from the Posix standard to
                           match the standard
              privileged   same as -p
              verbose      same as -v
              vi           use a vi-style line editing interface
              xtrace       same as -x
      -p  Turned on whenever the real and effective user ids do not match.
          Disables processing of the $ENV file and importing of shell
          functions.  Turning this option off causes the effective uid and
          gid to be set to the real uid and gid.
      -t  Exit after reading and executing one command.
      -u  Treat unset variables as an error when substituting.
      -v  Print shell input lines as they are read.
      -x  Print commands and their arguments as they are executed.
      -B  the shell will perform brace expansion
      -C  If set, disallow existing regular files to be overwritten
          by redirection of output.
      -E  If set, the ERR trap is inherited by shell functions.
      -H  Enable ! style history substitution.  This flag is on
          by default when the shell is interactive.
      -P  If set, do not follow symbolic links when executing commands
          such as cd which change the current directory.
      -T  If set, the DEBUG trap is inherited by shell functions.
      --  Assign any remaining arguments to the positional parameters.
          If there are no remaining arguments, the positional parameters
          are unset.
      -   Assign any remaining arguments to the positional parameters.
          The -x and -v options are turned off.
    
    Using + rather than - causes these flags to be turned off.  The
    flags can also be used upon invocation of the shell.  The current
    set of flags may be found in $-.  The remaining n ARGs are positional
    parameters and are assigned, in order, to $1, $2, .. $n.  If no
    ARGs are given, all shell variables are printed.
    
    Exit Status:
    Returns success unless an invalid option is given.
purpleEndurer @ cdu ~ $ 

这个信息与

Linux shell编程学习笔记28：脚本调试 set命令https://blog.csdn.net/Purpleendurer/article/details/134506337?spm=1001.2014.3001.5501中set --help命令显示的帮助信息是一致的。

3 查看bash内置的命令：bash -c help

purpleEndurer @ csdn ~ $ bash -c help
GNU bash, version 4.2.46(2)-release (x86_64-redhat-linux-gnu)
These shell commands are defined internally.  Type `help' to see this list.
Type `help name' to find out more about the function `name'.
Use `info bash' to find out more about the shell in general.
Use `man -k' or `info' to find out more about commands not in this list.

A star (*) next to a name means that the command is disabled.

 job_spec [&]                            history [-c] [-d offset] [n] or hist>
 (( expression ))                        if COMMANDS; then COMMANDS; [ elif C>
 . filename [arguments]                  jobs [-lnprs] [jobspec ...] or jobs >
 :                                       kill [-s sigspec | -n signum | -sigs>
 [ arg... ]                              let arg [arg ...]
 [[ expression ]]                        local [option] name[=value] ...
 alias [-p] [name[=value] ... ]          logout [n]
 bg [job_spec ...]                       mapfile [-n count] [-O origin] [-s c>
 bind [-lpvsPVS] [-m keymap] [-f filen>  popd [-n] [+N | -N]
 break [n]                               printf [-v var] format [arguments]
 builtin [shell-builtin [arg ...]]       pushd [-n] [+N | -N | dir]
 caller [expr]                           pwd [-LP]
 case WORD in [PATTERN [| PATTERN]...)>  read [-ers] [-a array] [-d delim] [->
 cd [-L|[-P [-e]]] [dir]                 readarray [-n count] [-O origin] [-s>
 command [-pVv] command [arg ...]        readonly [-aAf] [name[=value] ...] o>
 compgen [-abcdefgjksuv] [-o option]  >  return [n]
 complete [-abcdefgjksuv] [-pr] [-DE] >  select NAME [in WORDS ... ;] do COMM>
 compopt [-o|+o option] [-DE] [name ..>  set [-abefhkmnptuvxBCHP] [-o option->
 continue [n]                            shift [n]
 coproc [NAME] command [redirections]    shopt [-pqsu] [-o] [optname ...]
 declare [-aAfFgilrtux] [-p] [name[=va>  source filename [arguments]
 dirs [-clpv] [+N] [-N]                  suspend [-f]
 disown [-h] [-ar] [jobspec ...]         test [expr]
 echo [-neE] [arg ...]                   time [-p] pipeline
 enable [-a] [-dnps] [-f filename] [na>  times
 eval [arg ...]                          trap [-lp] [[arg] signal_spec ...]
 exec [-cl] [-a name] [command [argume>  true
 exit [n]                                type [-afptP] name [name ...]
 export [-fn] [name[=value] ...] or ex>  typeset [-aAfFgilrtux] [-p] name[=va>
 false                                   ulimit [-SHacdefilmnpqrstuvx] [limit>
 fc [-e ename] [-lnr] [first] [last] o>  umask [-p] [-S] [mode]
 fg [job_spec]                           unalias [-a] name [name ...]
 for NAME [in WORDS ... ] ; do COMMAND>  unset [-f] [-v] [name ...]
 for (( exp1; exp2; exp3 )); do COMMAN>  until COMMANDS; do COMMANDS; done
 function name { COMMANDS ; } or name >  variables - Names and meanings of so>
 getopts optstring name [arg]            wait [id]
 hash [-lr] [-p pathname] [-dt] [name >  while COMMANDS; do COMMANDS; done
 help [-dms] [pattern ...]               { COMMANDS ; }
purpleEndurer @ csdn ~ $ 

2 bash 命令行常用调试选项说明和演示

下面我们就bash命令行中的一些常用的调试选项逐一进行说明和演示。

2.1 echo $-：显示当前已启动的选项

purpleEndurer @ cdu ~ $ echo $-
himBH

purpleEndurer @ cdu ~ $

 可以看到，当前启用的选项有h、i、m、B和H这几个选项处于启动状态。

2.2 bash -n 脚本文件名说明符：不执行脚本，仅检查错误

-n 选项的功能是：读一遍脚本中的命令但不执行，用于检查脚本中的语法等错误。

2.2.1 创建测试脚本文件a.sh

我们用 cp 命令来创建 ，文件内容是： echo 'Hello world

为了测试，我们故意漏了命令行末尾配对的单引号。

purleEndurer @ csdn ~ $ cp /dev/stdin a.sh
echo 'Hello world   

 

2.2.2 查看测试脚本文件a.sh内容

purleEndurer @ csdn ~ $ cat a.sh
echo 'Hello world

2.2.3 检查脚本语法错误

purleEndurer @ csdn ~ $ bash -n a.sh
a.sh: line 1: unexpected EOF while looking for matching `''
a.sh: line 2: syntax error: unexpected end of file

 

可以看到，bash检查出a.sh存在两个错误。

第1个错误出现在第1行：寻找匹配的 ''' 时出现意外的 EOF，即单引号未配对。

第2个错误出现在第2行：语法错误：意外的文件结尾。

2.3 bash -x 脚本文件说明符：先显示命令及参数（不显示注释），再显示执行结果

bash命令的-x选项与set 命令中的-x选项功能相同，都是打开echo模式，执行命令后，会先显示该命令及所带的参数，再显示命令执行的结果：

2.3.1 创建测试脚本文件a.sh

我们用 cp 命令来创建 a.sh，文件内容如下：

purleEndurer @ csdn ~ $ cp /dev/stdin a.sh
echo -n Enter your name please:    # 提示用户输入名字
read n                             # 将用户输入的名字保存到变量n                                                                            
echo Your name is $n               # 显示用户输入的名字      

#号后的内容是对命令功能的说明。

2.3.2 执行脚本文件a.sh

purleEndurer @ csdn ~ $ bash -x a.sh
+ echo -n Enter your name please:
Enter your name please:+ read n
purpleEndurer
+ echo Your name is purpleEndurer
Your name is purpleEndurer
purleEndurer @ csdn ~ $ 

bash会将以+开头，将执行的命令显示出来，然后再显示命令执行的结果。

2.3.3 使用环境变量PS4定制显示格式

其实我们在使用bash的 -x选项来显示命令和参数时前面加的 + 是环境变量PS4 保存的。

purpleEndurer @csdn ~ $ set | grep PS4
PS4='+ '

因此，我们可以通过修改环境变量PS4的值来设置 bash的 -x选项显示命令和参数时的格式。

例如：我们对显示的命令和参数以 > 开头，然后引入${BASH_SOURCE} 显示脚本文件名，${LINENO}显示行号，${FUNCNAME[0]}显示正在执行的函数的名字：

purpleEndurer @csdn ~ $ PS1="\e[35mpurpleEndurer\e[0m @csdn \w $ "

purpleEndurer @csdn ~ $ export PS4='>${BASH_SOURCE}  [${LINENO}] ${FUNCNAME[0]}: '
purpleEndurer @csdn ~ $ bash -x a.sh
>a.sh  [1] : echo -n Enter your name please:
Enter your name please:>a.sh  [2] : read n
abc
>a.sh  [3] : echo Your name is abc
Your name is abc
purpleEndurer @csdn ~ $ 

如果觉得字符太多，不容易辨别的话，我们还可以分别给它们加上颜色：

purpleEndurer @csdn ~ $ export PS4='\e[35m>${BASH_SOURCE} \e[0m \e[33m [${LINENO}]\e[0m \e[31m ${FUNCNAME[0]}: \e[0m'
purpleEndurer @csdn ~ $ bash -x a.sh
>a.sh   [1]  : echo -n Enter your name please:
Enter your name please:>a.sh   [2]  : read n
abc
>a.sh   [3]  : echo Your name is abc
Your name is abc

这里我们使用了

Linux shell编程学习笔记4：修改命令行提示符格式（内容和颜色）https://blog.csdn.net/Purpleendurer/article/details/133416124?spm=1001.2014.3001.5501中介绍的知识，让脚本文件名以紫色显示，行号以黄色显示，正在执行的函数的名字以红色显示。

2.4 bash -v 脚本文件说明符：一边执行脚本，一边将执行过的脚本命令打印到标准输出（包括注释）

purpleEndurer @csdn ~ $ export PS4='\e[35m>${BASH_SOURCE} \e[0m \e[33m [${LINENO}]\e[0m \e[31m ${FUNCNAME[0]}: \e[0m'

purpleEndurer @csdn ~ $ bash -v a.sh
echo -n Enter your name please:    # 提示用户输入名字
Enter your name please:read n                             # 将用户输入的名字保存到变量n                                                                            
abc
echo Your name is $n               # 显示用户输入的名字 
Your name is abc
purpleEndurer @csdn ~ $ 

 可以看到，-v选项显示所执行的命令不受环境变量PS4的影响，而且会连脚本文件中的注释一并显示。