[Erlang 0031] Erlang Shell中的输出完整数据

前两天群里面有人问shell里面长数据被省略为 [...]|...],如何查看被省略的部分,他是在调用os:getenv()的时候遇到的这个问题,咱们前面也遇到过类似的问题,比如 string:tokens(binary_to_list(erlang:system_info(info)),"\n").

Eshell V5.9  (abort with ^G)
1>  string:tokens( binary_to_list(erlang:system_info(info)),"\n").
["=memory","total: 4331920","processes: 438877",
"processes_used: 438862","system: 3893043","atom: 146321",
"atom_used: 119102","binary: 327936","code: 1929551",
"ets: 123308","=hash_table:atom_tab","size: 4813",
"used: 3508","objs: 6410","depth: 7",
"=index_table:atom_tab","size: 7168","limit: 1048576",
"entries: 6410","=hash_table:module_code","size: 97",
"used: 52","objs: 72","depth: 4","=index_table:module_code",
"size: 1024","limit: 65536","entries: 72",
[...]|...]

当时我在群里面给了一个不标准的解决方法:binary_to_list(list_to_binary(os:getenv())).这个很野的路子是以前调试代码的时候偶尔发现的;

标准的解决方案是使用shell中的rp方法格式化输出结果 比如 rp(os:getenv()).特此修正,抱歉

9> L=lists:seq(1,100).
[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,
23,24,25,26,27,28,29|...]
10> rp(L).
[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,
23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,
43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,
63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,
83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100]
ok
11>

有必要了解一下shell中提供的方法:

Eshell V5.9  (abort with ^G)
1> help().
** shell internal commands **
b()        -- display all variable bindings
e(N)       -- repeat the expression in query <N>
f()        -- forget all variable bindings
f(X)       -- forget the binding of variable X
h()        -- history
history(N) -- set how many previous commands to keep
results(N) -- set how many previous command results to keep
catch_exception(B) -- how exceptions are handled
v(N)       -- use the value of query <N>
rd(R,D)    -- define a record
rf()       -- remove all record information
rf(R)      -- remove record information about R
rl()       -- display all record information
rl(R)      -- display record information about R
rp(Term)   -- display Term using the shell's record information
rr(File)   -- read record information from File (wildcards allowed)
rr(F,R)    -- read selected record information from file(s)
rr(F,R,O)  -- read selected record information with options
** commands in module c **
bt(Pid)    -- stack backtrace for a process
c(File)    -- compile and load code in <File>
cd(Dir)    -- change working directory
flush()    -- flush any messages sent to the shell
help()     -- help info
i()        -- information about the system
ni()       -- information about the networked system
i(X,Y,Z)   -- information about pid <X,Y,Z>
l(Module)  -- load or reload module
lc([File]) -- compile a list of Erlang modules
ls()       -- list files in the current directory
ls(Dir)    -- list files in directory <Dir>
m()        -- which modules are loaded
m(Mod)     -- information about module <Mod>
memory()   -- memory allocation information
memory(T)  -- memory allocation information of type <T>
nc(File)   -- compile and load code in <File> on all nodes
nl(Module) -- load module on all nodes
pid(X,Y,Z) -- convert X,Y,Z to a Pid
pwd()      -- print working directory
q()        -- quit - shorthand for init:stop()
regs()     -- information about registered processes
nregs()    -- information about all registered processes
xm(M)      -- cross reference check a module
y(File)    -- generate a Yecc parser
** commands in module i (interpreter interface) **
ih()       -- print help for the i module
true
2>

这些方法的内部实现为:

bi(I)           -> c:bi(I).
bt(Pid)          -> c:bt(Pid).
c(File)      -> c:c(File).
c(File, Opt)    -> c:c(File, Opt).
cd(D)           -> c:cd(D).
erlangrc(X)      -> c:erlangrc(X).
flush()         -> c:flush().
i()           -> c:i().
i(X,Y,Z)      -> c:i(X,Y,Z).
l(Mod)            -> c:l(Mod).
lc(X)            -> c:lc(X).
ls()            -> c:ls().
ls(S)           -> c:ls(S).
m()           -> c:m().
m(Mod)           -> c:m(Mod).
memory()        -> c:memory().
memory(Type)    -> c:memory(Type).
nc(X)          -> c:nc(X).
ni()            -> c:ni().
nl(Mod)      -> c:nl(Mod).
nregs()         -> c:nregs().
pid(X,Y,Z)      -> c:pid(X,Y,Z).
pwd()           -> c:pwd().
q()          -> c:q().
regs()          -> c:regs().
xm(Mod)         -> c:xm(Mod).
y(File)         -> c:y(File).
y(File, Opts)   -> c:y(File, Opts).

代码参见:http://www.google.com/codesearch#dNzC48WMK6w/lib/stdlib/src/shell_default.erl&ct=rc&cd=1&q=shell_default%20lang:erlang

晚安!