[tansheng@localhost ~]$ help

GNU bash, version 4.1.()-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] [dir]                        readarray [-n count] [-O origin] [-s>

 command [-pVv] command [arg ...]        readonly [-af] [name[=value] ...] or>

[tansheng@localhost ~]$ help fg

fg: fg [job_spec]

    Move job to the foreground.

    Place the job identified by JOB_SPEC in the foreground, making it the

    current job.  If JOB_SPEC is not present, the shell's notion of the

    current job is used.

    Exit Status:

    Status of command placed in foreground, or failure if an error occurs.

[tansheng@localhost ~]$ 

[tansheng@localhost ~]$ help alias

alias: alias [-p] [name[=value] ... ]

    Define or display aliases.

    Without arguments, `alias' prints the list of aliases in the reusable

    form `alias NAME=VALUE' on standard output.

    Otherwise, an alias is defined for each NAME whose VALUE is given.

    A trailing space in VALUE causes the next word to be checked for

    alias substitution when the alias is expanded.

    Options:

      -p    Print all defined aliases in a reusable format

    Exit Status:

    alias returns true unless a NAME is supplied for which no alias has been

    defined.

[tansheng@localhost ~]$