local shell=require("shell")
local args,options=shell.parse(...)

local ec,error_prefix=0,"alias:"

if options.help then
print(string.format("Usage: alias: [name[=value] ... ]"))
return
end

local function validAliasName(k)
return k:match("[/%$`=|&;%(%)<> \t]")==nil
end

local function setAlias(k,v)
if not validAliasName(k)then
io.stderr:write(string.format("%s `%s': invalid alias name\n",error_prefix,k))
else
shell.setAlias(k,v)
end
end

local function printAlias(k)
local v=shell.getAlias(k)
if not v then
io.stderr:write(string.format("%s %s: not found\n",error_prefix,k))
ec=1
else
io.write(string.format("alias %s='%s'\n",k,v))
end
end

local function splitPair(arg)
local matchBegin,matchEnd=arg:find("=")
if matchBegin==nil or matchBegin==1 then
return arg
else
return arg:sub(1,matchBegin-1),arg:sub(matchEnd+1)
end
end

local function handlePair(k,v)
if v then
return setAlias(k,v)
else
return printAlias(k)
end
end

if not next(args)then

for k,v in shell.aliases()do
print(string.format("alias %s='%s'",k,v))
end
else
for _,v in ipairs(args)do
checkArg(1,v,"string")
handlePair(splitPair(v))
end
end

return ec