从 bash 变量为 Erlang erl 传递 -eval 失败

Question

我正在尝试从 bash 脚本启动 erl。当我传递来自变量 erl 的 eval 表达式内容时，无法启动。当直接使用 eval 选项时在 erl 命令行中给出，erl 启动时没有任何问题。怎么做正确？

#!/bin/bash 
echo "-----------------------------------"
#
# Fails 
EVAL_EXP1="\"ok, observer:start(), ok\""
echo $EVAL_EXP1
erl -eval $EVAL_EXP1
#
# Fails 
echo "-----------------------------------"
EVAL_EXP2="ok, observer:start(), ok"
echo $EVAL_EXP2
erl -eval $EVAL_EXP2
#
# Works 
echo "-----------------------------------"
erl -eval "ok, observer:start(), ok"

脚本输出为

   13:30 $ ./start.sh 
   -----------------------------------
   "ok, observer:start(), ok"
   Crash dump is being written to: erl_crash.dump...done
   System process <0.0.0> terminated: {function_clause,   
   [{init,prepare_run_args,[{eval,[<<"\"ok,">>,<<"observer:start(),">>,  
   <<"ok\"">>]}],[]},{init,map,2,[]},{init,boot,1,[]}]}
   ./start.sh: line 7: 26573 Aborted     (core dumped) erl -eval $EVAL_EXP1
   -----------------------------------
   ok, observer:start(), ok
   (no error logger present) error: <0.0.0>

   Crash dump is being written to: erl_crash.dump...done
   System process <0.0.0> terminated: {function_clause,  
   [{init,prepare_run_args,[{eval,[<<"ok,">>,<<"observer:start(),">>,
   <<"ok">>]}],[]},{init,map,2,[]},{init,boot,1,[]}]}
   ./start.sh: line 13: 26599 Aborted                 (core dumped) erl -eval 
   $EVAL_EXP2
   -----------------------------------
   Erlang/OTP 18 [erts-7.0] [source] [64-bit] [smp:4:4] [async-threads:10]   
   [kernel-poll:false]

   Eshell V7.0  (abort with ^G)
   1>

Answer 1

您需要将变量替换用引号引起来，以便将它们作为单个参数发送给 erl:

EVAL_EXP2="ok, observer:start(), ok"
erl -eval "$EVAL_EXP2"

从 bash 变量为 Erlang erl 传递 -eval 失败

Passing -eval for Erlang erl from bash variable fails

bash

erlang

erl