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).
晚安!
