CMD List [11]
Arithmetic Function (awk)Option or argument
Function
atan2(y,x)
For nawk. Return the arctangent of y/x in radians.
cos(x)
Return the cosine of x
exp(arg)
Return the natural exponent of arg
int(arg)
Return the integer value of arg
log(arg)
Return the natural logarithm of arg
rand()
For nawk. Generate a random number between 0 and 1.
sin(x)
Return the sine of x
sqrt(arg)
Return square root of arg
srand(expr)
For nawk. Use expr to set a new seed for random number generator. Default is time of day.
e.g.
awk '{if($3~/48/) print $0}' grade.txt
who | awk '{print $1 " " $NF " is good."}'
Calculation & END
ls -l | awk '{ totalsize += $5; print totalsize }'
512
1024
2048
ls -l | awk '{ totalsize += $5; print totalsize }' | tail -1
ls -l | awk '{ totalsize += $5 } END { print totalsize }'
Script & Array & Looping – for
awkscript
{
count++
}
END {
for (i=1; i < 9; i++)
print “There are “ count “ accounts with “ i “ letter names.”
}
awk -F: -f awkscript < /etc/passwd
Condition – if
awk -F: ‘{ if (length($1) == 1) print $0 }’ < /etc/passwd
ls -l | awk '{if($1=="-rw-r-----") print $9}'
1 Error Message
M – message; S – solution.
M: &FILE=/sysp/cdclient/ndm/cfg/cliapi/ndmapi.cfg:&OSERR=13:&OSMSG=Permission denied
S: remove existing log.
2 Administration
2.1 Get Disk Space
Trimming a Directory - creating new files can make a directory bigger, deleting new files doesn't, it can never get smaller, unless you delete it.
e.g. 1. mv project project.toobig 2. mkdir project 3. mv project.toobig/*.txt project 4. rm -r project.toobig
Huge Files Might Not Take a Lot of Disk Space (if a lot of NUL characters in it), ls -ls to find the space allocation.
2.2 DOS ftp AIX
ftp <ip>
rename <original name> <new name>
put <local file> <remote file>
asc,pwd,dir,ls,rm,del,bye,Ctrl + C
3 Perl
Summary
1) Full name is “Practical Extraction and Report Language”. Slogan “There's More Than One Way To Do It”.
2) Automatically initialize variables and arrays start with a null or 0 value.
3) Like C, PERL statements must end in a semicolon (;).
4) Comments begin with a pound sign (#).
5) First line should mark with #!/usr/local/bin/perl. E.g.
#!/usr/bin/perl -w # prompt warning
6) list use (), string use ‘’ or “”.
7) compare with Double quotes (“”), Apostrophe (‘’): 1 – can’t replace variable 2 – 反斜线不支持转义字符. 3 – 可以跨多行.
'' – Single Quote / Apostrophe, string no variable replacement
"" - Double quotes, string with variable replacement
`` - Backquote / Backtick, run the command, generate output as input
8) Automatically transform string into numeric. E.g. $result = "12a34" +1; # $result = 13
Argument
-e
used to enter one line of program. If -e is given, Perl will not look for a filename in the argument list.
-p
A –p overrides a –n switch. It causes Perl to assume the following loop.
while (<>) {
... # your program goes here
} continue {
print or die "-p destination: $!\n";
}
Data Type
Scalars
纯量, string, number, or a reference. Denoted by $
Arrays of scalars
ordered lists of scalars indexed by number, starting with 0. Denoted by @. Arrays of scalars are faster than associative arrays.
Hashes
known as ‘associative arrays (of scalars)’, unordered collections of scalar indexed by string. Denoted by %
Note: Not divide data type into string, integer and float.
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