演示程序
#!/bin/sh -x
#由反引号括起来的也是一条命令，Shell先执行该命令，然后将输出结果立刻代换到当前命令行中。例如定义一个变量存放date命令的输出：
echo `date`
#命令代换也可以用$()表示：
echo $ ( date )
#如果一个变量叫做VARNAME，用${VARNAME}可以表示它的值，在不引起歧义的情况下也可以用$VARNAME表示它的值。通过以下例子比较这两种表示法的不同：
echo $SHELL
echo $SHELLabc
echo $ { SHELL } abc
#单引号用于保持引号内所有字符的字面值，即使引号内的\和回车也不例外，但是字符串中不能出现单引号
echo '$SHELL'
echo "$SHELL"
echo '$SHELL
hello world'
#双引号用于保持引号内所有字符的字面值（回车也不例外），除以下情况外：
#$加变量名可以取变量的值
#反引号仍表示命令替换
#\$表示$的字面值
#\`表示`的字面值
#\"表示"的字面值
#\\表示\的字面值
echo "$SHELL
hello world"
echo "\$SHELL
hello world"
#命令test或[可以测试一个条件是否成立，如果测试结果为真，则该命令的Exit Status为0，如果测试结果为假，则命令的Exit Status为1
VAR = 2
test $VAR - gt 1
echo $ ?
test $VAR - gt 3
echo $ ?
[ $VAR - gt 3 ]
echo $ ?
#存在Desktop目录且VAR等于abc
VAR = abc
[ - d Desktop - a $VAR = 'abc' ]
echo $ ?
#在Shell中用if、then、elif、else、fi这几条命令实现分支控制
echo "Is it morning? Please answer yes or no."
read YES_OR_NO
if [ "$YES_OR_NO" = "yes" ]; then
echo "Good morning!"
elif [ "$YES_OR_NO" = "no" ]; then
echo "Good afternoon!"
else
echo "Sorry, $YES_OR_NO not recognized. Enter yes or no."
exit 1
fi
#C语言的case只能匹配整型或字符型常量表达式，而Shell脚本的case可以匹配字符串和Wildcard，每个匹配分支可以有若干条命令，末尾为;;
echo "Is it morning? Please answer yes or no."
read YES_OR_NO
case "$YES_OR_NO" in
yes | y | Yes | YES )
echo "Good Morning!" ;;
[ nN ]*)
echo "Good Afternoon!" ;;
*)
echo "Sorry, $YES_OR_NO not recognized. Enter yes or no."
exit 1 ;;
esac
#FRUIT是一个循环变量，第一次循环$FRUIT的取值是apple，第二次取值是banana，第三次取值是pear
for FRUIT in apple banana pear ; do
echo "I like $FRUIT"
done
#while的用法和C语言类似
echo "Enter password:"
read TRY
while [ "$TRY" != "secret" ]; do
echo "Sorry, try again"
read TRY
done
COUNTER = 1
while [ "$COUNTER" - lt 10 ]; do
echo "COUNTER is $COUNTER"
COUNTER = $ (( $COUNTER + 1 ))
done
#$0 相当于C语言main函数的argv[0]
echo "The program $0 is now running"
#$1、$2... 这些称为位置参数（Positional Parameter），相当于C语言main函数的argv[1]、argv[2]...
echo "The first parameter is $1"
echo "The second parameter is $2"
$@ 表示参数列表 "$1" "$2" ...，例如可以用在 for 循环中的 in 后面
for PARAM in $@ ; do
echo "PARAM $PARAM"
done
echo "The parameter list is $@"
#位置参数可以用shift命令左移
shift
echo "The first parameter is $1"
echo "The second parameter is $2"
echo "The parameter list is $@"
#数就像是迷你脚本，调用函数时可以传任意个参数，在函数内同样是用$0、$1、$2等变量来提取参数
#函数中的位置参数相当于函数的局部变量，改变这些变量并不会影响函数外面的$0、$1、$2等变量
#函数中可以用return命令返回，如果return后面跟一个数字则表示函数的Exit Status
is_directory ()
{
DIR_NAME = $1
if [ ! - d $DIR_NAME ]; then
return 1
else
return 0
fi
}
for DIR in "$@" ; do
if is_directory "$DIR"
then :
else
echo "$DIR doesn't exist. Creating it now..."
mkdir $DIR > /dev/ null 2 >& 1
if [ $ ? - ne 0 ]; then
echo "Cannot create directory $DIR"
exit 1
fi
fi
done sh与bash区别
#!/bin/bash
diff <( echo xxx ) <( echo yyy ) # 此语法包含bash的特性，不属于sh的POSIX标准
[ wwy@sf - watch test ] $ bash - x ./ t2 . sh # 使用bash 调用，不会出问题
+ diff / dev / fd / 63 / dev / fd / 62
++ echo xxx
++ echo yyy
1c1
< xxx
---
> yyy
[ wwy@sf - watch test ] $ sh ./ t2 . sh # 而用sh调用，报错如下
./ t2 . sh : line 3 : syntax error near unexpected token `('
./t2.sh: line 3: ` diff <( echo xxx ) <( echo yyy ) '
[wwy@sf-watch test]$ echo $?
long invocation options
[+-] O invocation option
- l invocation option
`!' reserved word to invert pipeline return value
` time ' reserved word to time pipelines and shell builtins
the `function' reserved word
the `select' compound command and reserved word
arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
new $'...' and $"..." quoting
the $(...) form of command substitution
the $(<filename) form="" of="" command="" substitution,="" equivalent="" to
$(cat filename)
the ${#param} parameter value length operator
the ${!param} indirect parameter expansion operator
the ${!param*} prefix expansion operator
the ${param:offset[:length]} parameter substring operator
the ${param/pat[/string]} parameter pattern substitution operator
expansions to perform substring removal (${p%[%]w}, ${p#[#]w})
expansion of positional parameters beyond $9 with ${num}
variables: BASH, BASH_VERSION, BASH_VERSINFO, UID, EUID, REPLY,
TIMEFORMAT, PPID, PWD, OLDPWD, SHLVL, RANDOM, SECONDS,
LINENO, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE, HOSTNAME,
ENV, PS3, PS4, DIRSTACK, PIPESTATUS, HISTSIZE, HISTFILE,
HISTFILESIZE, HISTCONTROL, HISTIGNORE, GLOBIGNORE, GROUPS,
PROMPT_COMMAND, FCEDIT, FIGNORE, IGNOREEOF, INPUTRC,
SHELLOPTS, OPTERR, HOSTFILE, TMOUT, FUNCNAME, histchars,
auto_resume
DEBUG trap
ERR trap
variable arrays with new compound assignment syntax
redirections: <>, &>, >|, <<<, [n]<&word-, [n]>&word-
prompt string special char translation and variable expansion
auto-export of variables in initial environment
command search finds functions before builtins
bash return builtin will exit a file sourced with ` . '
builtins: cd -/-L/-P, exec -l/-c/-a, echo -e/-E, hash -d/-l/-p/-t.
export -n/-f/-p/name=value, pwd -L/-P,
read -e/-p/-a/-t/-n/-d/-s/-u,
readonly -a/-f/name=value, trap -l, set +o,
set -b/-m/-o option/-h/-p/-B/-C/-H/-P,
unset -f/-v, ulimit -i/-m/-p/-q/-u/-x,
type -a/-p/-t/-f/-P, suspend -f, kill -n,
test -o optname/s1 == s2/s1 < s2/s1 > s2/-nt/-ot/-ef/-O/-G/-S
bash reads ~/.bashrc for interactive shells, $ENV for non-interactive
bash restricted shell mode is more extensive
bash allows functions and variables with the same name
brace expansion
tilde expansion
arithmetic expansion with $((...)) and `let' builtin
the `[[...]]' extended conditional command
process substitution
aliases and alias/unalias builtins
local variables in functions and ` local ' builtin
readline and command-line editing with programmable completion
command history and history/fc builtins
csh-like history expansion
other new bash builtins: bind, command, compgen, complete, builtin,
declare/typeset, dirs, enable, fc, help,
history, logout, popd, pushd, disown, shopt,
printf
exported functions
filename generation when using output redirection (command >a*)
POSIX.2-style globbing character classes
POSIX.2-style globbing equivalence classes
POSIX.2-style globbing collating symbols
egrep-like extended pattern matching operators
case-insensitive pattern matching and globbing
variable assignments preceding commands affect only that command,
even for builtins and functions
posix mode and strict posix conformance
redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr,
/dev/tcp/host/port, /dev/udp/host/port
debugger support, including `caller' builtin and new variables
RETURN trap
the `+=' assignment operator
Things sh has that bash does not:
uses variable SHACCT to do shell accounting
includes ` stop ' builtin (bash can use alias stop=' kill - s STOP ')
`newgrp' builtin
turns on job control if called as `jsh'
$TIMEOUT (like bash $TMOUT)
` ^ ' is a synonym for `|'
new SVR4 . 2 sh builtins : mldmode , priv
Implementation differences :
redirection to / from compound commands causes sh to create a subshell
bash does not allow unbalanced quotes ; sh silently inserts them at EOF
bash does not mess with signal 11
sh sets ( euid , egid ) to ( uid , gid ) if - p not supplied and uid < 100
bash splits only the results of expansions on IFS , using POSIX . 2
field splitting rules ; sh splits all words on IFS
sh does not allow MAILCHECK to be unset (?)
sh does not allow traps on SIGALRM or SIGCHLD
bash allows multiple option arguments when invoked ( e . g . - x - v );
sh allows only a single option argument ( `sh -x -v' attempts
to open a file named ` - v ', and, on SunOS 4.1.4, dumps core.
On Solaris 2.4 and earlier versions, sh goes into an infinite
loop.)
sh exits a script if any builtin fails; bash exits only if one of
the POSIX.2 `special' builtins fails
~ /.bash_profile（ -> ~/ . bashrc -> /etc/ bashrc ）
~ /.bash_login
~/ . profile
~ /.bash_profile （ -> ~/ . bashrc -> /etc/ bashrc ）
~ /.bash_login
~/ . profile
$BASH_ENV
SH ：
~/. profile
~/. profile
ulimit - S - c unlimited > /dev/ null 2 >& 1
wangweiyu@127 . 0.0 . 1 's password:
hBc
[wangweiyu@ComSeOp ~]$ echo $-
himBH
[wangweiyu@ComSeOp ~]$ ssh wangweiyu@127.0.0.1 ' echo $0 '
wangweiyu@127.0.0.1' s password :
bash
[ wangweiyu@ComSeOp ~] $ echo $0
- bash
# .bashrc
# User specific aliases and functions
# Source global definitions
if [ - f / etc / bashrc ]; then
. / etc / bashrc
fi
echo 'xxx'
[ wangweiyu@ComSeOp ~] $ ssh wangweiyu@127 . 0.0 . 1 'echo $-'
wangweiyu@127 . 0.0 . 1 's password:
xxx
hBc
# .bashrc
# User specific aliases and functions
# Source global definitions
if [ - f / etc / bashrc ]; then
. / etc / bashrc
fi
echo 'xxx'
[ wangweiyu@ComSeOp ~] $ scp file wangweiyu@127 . 0.0 . 1 : /tmp
wangweiyu@127.0.0.1's password:
xxx
[wangweiyu@ComSeOp ~]$ echo $?
1
[wangweiyu@ComSeOp ~]$ ls / tmp /
[ wangweiyu@ComSeOp ~] $
#由反引号括起来的也是一条命令，Shell先执行该命令，然后将输出结果立刻代换到当前命令行中。例如定义一个变量存放date命令的输出：
echo `date`
#命令代换也可以用$()表示：
echo $ ( date )
#如果一个变量叫做VARNAME，用${VARNAME}可以表示它的值，在不引起歧义的情况下也可以用$VARNAME表示它的值。通过以下例子比较这两种表示法的不同：
echo $SHELL
echo $SHELLabc
echo $ { SHELL } abc
#单引号用于保持引号内所有字符的字面值，即使引号内的\和回车也不例外，但是字符串中不能出现单引号
echo '$SHELL'
echo "$SHELL"
echo '$SHELL
hello world'
#双引号用于保持引号内所有字符的字面值（回车也不例外），除以下情况外：
#$加变量名可以取变量的值
#反引号仍表示命令替换
#\$表示$的字面值
#\`表示`的字面值
#\"表示"的字面值
#\\表示\的字面值
echo "$SHELL
hello world"
echo "\$SHELL
hello world"
#命令test或[可以测试一个条件是否成立，如果测试结果为真，则该命令的Exit Status为0，如果测试结果为假，则命令的Exit Status为1
VAR = 2
test $VAR - gt 1
echo $ ?
test $VAR - gt 3
echo $ ?
[ $VAR - gt 3 ]
echo $ ?
#存在Desktop目录且VAR等于abc
VAR = abc
[ - d Desktop - a $VAR = 'abc' ]
echo $ ?
#在Shell中用if、then、elif、else、fi这几条命令实现分支控制
echo "Is it morning? Please answer yes or no."
read YES_OR_NO
if [ "$YES_OR_NO" = "yes" ]; then
echo "Good morning!"
elif [ "$YES_OR_NO" = "no" ]; then
echo "Good afternoon!"
else
echo "Sorry, $YES_OR_NO not recognized. Enter yes or no."
exit 1
fi
#C语言的case只能匹配整型或字符型常量表达式，而Shell脚本的case可以匹配字符串和Wildcard，每个匹配分支可以有若干条命令，末尾为;;
echo "Is it morning? Please answer yes or no."
read YES_OR_NO
case "$YES_OR_NO" in
yes | y | Yes | YES )
echo "Good Morning!" ;;
[ nN ]*)
echo "Good Afternoon!" ;;
*)
echo "Sorry, $YES_OR_NO not recognized. Enter yes or no."
exit 1 ;;
esac
#FRUIT是一个循环变量，第一次循环$FRUIT的取值是apple，第二次取值是banana，第三次取值是pear
for FRUIT in apple banana pear ; do
echo "I like $FRUIT"
done
#while的用法和C语言类似
echo "Enter password:"
read TRY
while [ "$TRY" != "secret" ]; do
echo "Sorry, try again"
read TRY
done
COUNTER = 1
while [ "$COUNTER" - lt 10 ]; do
echo "COUNTER is $COUNTER"
COUNTER = $ (( $COUNTER + 1 ))
done
#$0 相当于C语言main函数的argv[0]
echo "The program $0 is now running"
#$1、$2... 这些称为位置参数（Positional Parameter），相当于C语言main函数的argv[1]、argv[2]...
echo "The first parameter is $1"
echo "The second parameter is $2"
$@ 表示参数列表 "$1" "$2" ...，例如可以用在 for 循环中的 in 后面
for PARAM in $@ ; do
echo "PARAM $PARAM"
done
echo "The parameter list is $@"
#位置参数可以用shift命令左移
shift
echo "The first parameter is $1"
echo "The second parameter is $2"
echo "The parameter list is $@"
#数就像是迷你脚本，调用函数时可以传任意个参数，在函数内同样是用$0、$1、$2等变量来提取参数
#函数中的位置参数相当于函数的局部变量，改变这些变量并不会影响函数外面的$0、$1、$2等变量
#函数中可以用return命令返回，如果return后面跟一个数字则表示函数的Exit Status
is_directory ()
{
DIR_NAME = $1
if [ ! - d $DIR_NAME ]; then
return 1
else
return 0
fi
}
for DIR in "$@" ; do
if is_directory "$DIR"
then :
else
echo "$DIR doesn't exist. Creating it now..."
mkdir $DIR > /dev/ null 2 >& 1
if [ $ ? - ne 0 ]; then
echo "Cannot create directory $DIR"
exit 1
fi
fi
done sh与bash区别
在我们所使用的系统当中，使用sh调用执行脚本，相当于打开了bash的POSIX标准模式 （等效于bash的 --posix 参数）
一般的，sh是bash的“子集” （不是子集的部分，具体区别见下的“Things sh has that bash does not”）
例子：
[ wwy@sf - watch test ] $ cat t2 . sh#!/bin/bash
diff <( echo xxx ) <( echo yyy ) # 此语法包含bash的特性，不属于sh的POSIX标准
[ wwy@sf - watch test ] $ bash - x ./ t2 . sh # 使用bash 调用，不会出问题
+ diff / dev / fd / 63 / dev / fd / 62
++ echo xxx
++ echo yyy
1c1
< xxx
---
> yyy
[ wwy@sf - watch test ] $ sh ./ t2 . sh # 而用sh调用，报错如下
./ t2 . sh : line 3 : syntax error near unexpected token `('
./t2.sh: line 3: ` diff <( echo xxx ) <( echo yyy ) '
[wwy@sf-watch test]$ echo $?
2
但是，在我们的linux系统中，sh是bash的一个软链接：
mon$ which sh /bin/sh mon$ ls -l /bin/sh lrwxrwxrwx 1 root root 4 Mar 21 2007 /bin/sh -> bash
那为什么上面的例子中还会出现问题呢？原因在于： bash程序执行，当“$0”是“sh”的时候，则要求下面的代码遵循一定的规范，当不符合规范的语法存在时，则会报错， 所以可以这样理解， “sh”并不是一个程序，而是一种标准（POSIX），这种标准，在一定程度上保证了脚本的跨系统性（跨UNIX系统）
下面的内容详细的说明了bash与sh在语法等方面的具体差异：
Things bash has that sh does not :long invocation options
[+-] O invocation option
- l invocation option
`!' reserved word to invert pipeline return value
` time ' reserved word to time pipelines and shell builtins
the `function' reserved word
the `select' compound command and reserved word
arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
new $'...' and $"..." quoting
the $(...) form of command substitution
the $(<filename) form="" of="" command="" substitution,="" equivalent="" to
$(cat filename)
the ${#param} parameter value length operator
the ${!param} indirect parameter expansion operator
the ${!param*} prefix expansion operator
the ${param:offset[:length]} parameter substring operator
the ${param/pat[/string]} parameter pattern substitution operator
expansions to perform substring removal (${p%[%]w}, ${p#[#]w})
expansion of positional parameters beyond $9 with ${num}
variables: BASH, BASH_VERSION, BASH_VERSINFO, UID, EUID, REPLY,
TIMEFORMAT, PPID, PWD, OLDPWD, SHLVL, RANDOM, SECONDS,
LINENO, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE, HOSTNAME,
ENV, PS3, PS4, DIRSTACK, PIPESTATUS, HISTSIZE, HISTFILE,
HISTFILESIZE, HISTCONTROL, HISTIGNORE, GLOBIGNORE, GROUPS,
PROMPT_COMMAND, FCEDIT, FIGNORE, IGNOREEOF, INPUTRC,
SHELLOPTS, OPTERR, HOSTFILE, TMOUT, FUNCNAME, histchars,
auto_resume
DEBUG trap
ERR trap
variable arrays with new compound assignment syntax
redirections: <>, &>, >|, <<<, [n]<&word-, [n]>&word-
prompt string special char translation and variable expansion
auto-export of variables in initial environment
command search finds functions before builtins
bash return builtin will exit a file sourced with ` . '
builtins: cd -/-L/-P, exec -l/-c/-a, echo -e/-E, hash -d/-l/-p/-t.
export -n/-f/-p/name=value, pwd -L/-P,
read -e/-p/-a/-t/-n/-d/-s/-u,
readonly -a/-f/name=value, trap -l, set +o,
set -b/-m/-o option/-h/-p/-B/-C/-H/-P,
unset -f/-v, ulimit -i/-m/-p/-q/-u/-x,
type -a/-p/-t/-f/-P, suspend -f, kill -n,
test -o optname/s1 == s2/s1 < s2/s1 > s2/-nt/-ot/-ef/-O/-G/-S
bash reads ~/.bashrc for interactive shells, $ENV for non-interactive
bash restricted shell mode is more extensive
bash allows functions and variables with the same name
brace expansion
tilde expansion
arithmetic expansion with $((...)) and `let' builtin
the `[[...]]' extended conditional command
process substitution
aliases and alias/unalias builtins
local variables in functions and ` local ' builtin
readline and command-line editing with programmable completion
command history and history/fc builtins
csh-like history expansion
other new bash builtins: bind, command, compgen, complete, builtin,
declare/typeset, dirs, enable, fc, help,
history, logout, popd, pushd, disown, shopt,
printf
exported functions
filename generation when using output redirection (command >a*)
POSIX.2-style globbing character classes
POSIX.2-style globbing equivalence classes
POSIX.2-style globbing collating symbols
egrep-like extended pattern matching operators
case-insensitive pattern matching and globbing
variable assignments preceding commands affect only that command,
even for builtins and functions
posix mode and strict posix conformance
redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr,
/dev/tcp/host/port, /dev/udp/host/port
debugger support, including `caller' builtin and new variables
RETURN trap
the `+=' assignment operator
Things sh has that bash does not:
uses variable SHACCT to do shell accounting
includes ` stop ' builtin (bash can use alias stop=' kill - s STOP ')
`newgrp' builtin
turns on job control if called as `jsh'
$TIMEOUT (like bash $TMOUT)
` ^ ' is a synonym for `|'
new SVR4 . 2 sh builtins : mldmode , priv
Implementation differences :
redirection to / from compound commands causes sh to create a subshell
bash does not allow unbalanced quotes ; sh silently inserts them at EOF
bash does not mess with signal 11
sh sets ( euid , egid ) to ( uid , gid ) if - p not supplied and uid < 100
bash splits only the results of expansions on IFS , using POSIX . 2
field splitting rules ; sh splits all words on IFS
sh does not allow MAILCHECK to be unset (?)
sh does not allow traps on SIGALRM or SIGCHLD
bash allows multiple option arguments when invoked ( e . g . - x - v );
sh allows only a single option argument ( `sh -x -v' attempts
to open a file named ` - v ', and, on SunOS 4.1.4, dumps core.
On Solaris 2.4 and earlier versions, sh goes into an infinite
loop.)
sh exits a script if any builtin fails; bash exits only if one of
the POSIX.2 `special' builtins fails
调用相关：
在脚本的调用方面（interactive、login相关），bash与sh也是存在差异 以下是详细说明（假如被调用执行的脚本名字叫xxx.sh）
BASH： 1、 交互式的登录shell （bash –il xxx.sh） 载入的信息：
/etc/ profile~ /.bash_profile（ -> ~/ . bashrc -> /etc/ bashrc ）
~ /.bash_login
~/ . profile
2、非交互式的登录shell （bash –l xxx.sh） 载入的信息：
/etc/ profile~ /.bash_profile （ -> ~/ . bashrc -> /etc/ bashrc ）
~ /.bash_login
~/ . profile
$BASH_ENV
3、交互式的非登录shell （bash –i xxx.sh） 载入的信息：
~ /.bashrc （ -> / etc / bashrc ）4、非交互式的非登录shell （bash xxx.sh） 载入的信息：
$BASH_ENVSH ：
1、交互式的登录shell 载入的信息：
/etc/ profile~/. profile
2、非交互式的登录shell 载入的信息：
/etc/ profile~/. profile
3、交互式的非登录shell 载入的信息：
$ENV4、非交互式的非登录shell 载入的信息： nothing
由此可以看出，最主要的区别在于相关配置文件的是否载入， 而这些配置的是否载入，也就导致了很多默认选项的差异 （具体请仔细查看~/.bash_profile 等文件） 如：
[ wangweiyu@ComSeOp ~] $ grep ulimit / etc / profileulimit - S - c unlimited > /dev/ null 2 >& 1
即，如果/etc/profile没有被载入，则不会产生core dump
值得一提的是，使用ssh远程执行命令， 远端sshd进程通过“bash –c”的方式来执行命令（即“非交互式的非登录shell”） 所以这一点，和登录之后再在本地执行执行命令，就存在了一定的差异
如：
[ wangweiyu@ComSeOp ~] $ ssh wangweiyu@127 . 0.0 . 1 'echo $-'wangweiyu@127 . 0.0 . 1 's password:
hBc
[wangweiyu@ComSeOp ~]$ echo $-
himBH
[wangweiyu@ComSeOp ~]$ ssh wangweiyu@127.0.0.1 ' echo $0 '
wangweiyu@127.0.0.1' s password :
bash
[ wangweiyu@ComSeOp ~] $ echo $0
- bash
注： “$-” 中含有“i”代表“交互式shell” “$0”的显示结果为“-bash”，bash前面多个“-”，代表“登录shell” 没有“i“和“-”的，是“非交互式的非登录shell”
另外还有一点，虽然ssh远程执行的命令是“非交互式的非登录shell”，但在执行命令之前，ssh的那一次登录本身是“交互式的登录shell”，所以其会先读一下“~/.bash_profile”
如：
[ wangweiyu@ComSeOp ~] $ cat . bashrc# .bashrc
# User specific aliases and functions
# Source global definitions
if [ - f / etc / bashrc ]; then
. / etc / bashrc
fi
echo 'xxx'
[ wangweiyu@ComSeOp ~] $ ssh wangweiyu@127 . 0.0 . 1 'echo $-'
wangweiyu@127 . 0.0 . 1 's password:
xxx
hBc
这一点，衍生出一个关于scp的问题，scp在传输数据之前，会先进行一次ssh登录， 而当.bashrc文件有输出的时候，则会导致scp失败！原因是解析返回的数据包出现混乱
如：
[ wangweiyu@ComSeOp ~] $ cat . bashrc# .bashrc
# User specific aliases and functions
# Source global definitions
if [ - f / etc / bashrc ]; then
. / etc / bashrc
fi
echo 'xxx'
[ wangweiyu@ComSeOp ~] $ scp file wangweiyu@127 . 0.0 . 1 : /tmp
wangweiyu@127.0.0.1's password:
xxx
[wangweiyu@ComSeOp ~]$ echo $?
1
[wangweiyu@ComSeOp ~]$ ls / tmp /
[ wangweiyu@ComSeOp ~] $
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