各shell 之间的差异
不同的shell 有不同的写法，以下是各个shell的比较：Feature
C/TC
Bourne
Bash
Korn
Variables:
Assigning values to local variables
set x = 5
x=5
x=5
x=5
Assigning variable attributes
declare or
typeset
typeset
Assigning values to environment variables
setenv NAME Bob
NAME='Bob'; export NAME
export NAME='Bob'
export NAME='Bob'
Read-Only Variables:
Accessing variables
echo $NAME
set var = net
echo ${var}work
network
echo $NAME
var=net
echo ${var}work
network
echo $NAME
var=net
echo ${var}work
network
echo $NAME or print $NAME
var=net
print ${var}work
network
Number of characters
echo $%var (tcsh only)
N/A
${#var}
${#var}
Special Variables:
PID of the process
$$
$$
$$
$$
Exit status
$status, $?
$?
$?
$?
Last background job
$! (tcsh only)
$!
$!
$!
Arrays:
Assigning arrays
set x = ( a b c )
N/A
y='a'; y='b'; y='c'
fruit=(apples pears peaches plums)
y='a'; y='b'; y='c'
set –A fruit apples pears plums
Accessing array elements
echo $x $x
N/A
echo ${y} ${y}
print ${y} ${y}
All elements
echo $x or $x
[*]
N/A
echo ${y
[*]}, ${fruit}
print ${y
[*]}, ${fruit}
No. of elements
echo $#x
N/A
echo $y{#
[*]}
print ${#y
[*]}
Command Substitution:
Assigning output of command to variable
set d = `date`
d=`date`
d=$(date) or d=`date`
d=$(date) or d=`date`
Accessing values
echo $d
echo $d, $d,
...
echo $#d
echo $d
echo $d
print $d
Command Line Arguments (Positional Parameters):
Accessing
$argv, $argvor
$1, $2 ...
$1, $2 ... $9
$1, $2, ... ${10} ...
$1, $2, ... ${10} ...
Setting positional parameters
N/A
set ab c
set `date`
echo $1 $2 ...
set ab c
set `date` or set $(date)
echo $1 $2 ...
set abc
set `date` or set $(date)
print $1 $2 ...
No. of command line arguments
$#argv
$# (tcsh)
$#
$#
$#
No. of characters in $arg
$%1, $%2, (tcsh)
N/A
N/A
N/A
Metacharacters for Filename Expansion:
Matches for:
Single character
?
?
?
?
Zero or more characters
*
*
*
*
One character from a set
One character from a range of characters in a set
One character not in the set
N/A(csh)
[^abc](tcsh)
[!abc]
[!abc]
[!abc]
? matches zero or one occurrences of any pattern in the parentheses. The vertical bar represents an OR condition; e.g., either 2 or 9. Matches abc21, abc91, or abc1.
abc?(2|9)1
abc?(2|9)1
Filenames not matching a pattern
^pattern (tcsh)
I/O Redirection and Pipes:
Command output redirected to a file
cmd > file
cmd > file
cmd > file
cmd > file
Command output redirected and appended to a file
cmd >> file
cmd >> file
cmd >> file
cmd >> file
Command input redirected from a file
cmd < file
cmd < file
cmd < file
cmd < file
Command errors redirected to a file
(cmd > /dev/tty)>&errors
cmd 2>errors
cmd 2> file
cmd 2> errors
Output and errors redirected to a file
cmd >& file
cmd > file 2>&1
cmd >& file or cmd &> file or cmd > file 2>&1
cmd > file 2>&1
Assign output and ignore noclobber
cmd >| file
N/A
cmd >| file
cmd >| file
here document
cmd
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