In shell code you are concerned about: efficiency and readability
The former because you want to minimize the impact of your code on the system, the latter because you and others will have to change this stuff X years from now when you have completely forgotten about it, and it no longer works the way you need.
Either of these is equally fast:
The first one is more conventional, and is more likely to port.
[ is a bash builtin, [[ is a keyword so they both run as part of the shell, as does (( )).
So it boils down to which one is the easiest to for another person to interpret, which is a personal matter.
This User Gave Thanks to jim mcnamara For This Post:
Hello folks,
I have data collected in every 3 hours. But, I would like to expand this to 1 hour interval by equally dividing with next row.
For example, I want to keep the first value 1987-01-01-00z 2.0, but following all record should be re-written as follow.
1987-01-01-03z 5.0 becomes... (11 Replies)
I am trying to setup to automatically import a series of mysql database files. I am doing manually now and its a royal pain.
All the sql files are sequentially numbered in a format of 4 numbers underscore text with spaces replaced by underscores.
example:
There are 3 databases each setup... (1 Reply)
Is there an easy way using a command or other routine for testing whether an argument on the command line is numeric? Just want to validate... I ran a search and didn't find a similar question....
Thx (3 Replies)
Can someone tell me how to change the first column in a very large 17k line file from a random 10 digit numeric value to a non numeric value. The format of lines in the file is:
1702938475,SNU022,201004
the first 10 numbers always begin with 170 (6 Replies)
Hi,
I'm quite new to scripting, but know a few AWK statements.
I have the following line in my script:
hostname=`echo $file | awk 'BEGIN{FS=OFS="."}{$NF=""; NF--; print}'`
I use this in my script to rename files, which are similar to this:
name.mvkf.mkvfm.mkfvm.1
To the... (4 Replies)
hey,
I have text file which has some data for some device Id's. i want to perform AVG, MAX,2nd MAX on these device ids. The .txt file looks like below. please help me in finding the computations per Device id. My output file should contatin with DeviceID,Avg, max and 2nd max of the device ID.... (8 Replies)
Hi All,
I have a file menu_opts is as follows
# cat menu_opts
Please select the options
qqqq_usb STD RETAIL Progs (Prime time cue advertisements)
qqqq_onc STD Dealer Progs (Prime time cue advertisements)
qqqq_zt_usb STD RETAIL Progs (Long Format cue... (2 Replies)
I have the following code and into into trying to simplifying it. Any suggestions please?
pmin = min (p(1), p(2), p(3), p(4), p(5), p(6))
ni = 0
xint = 0.0
yint = 0.0
zint = 0.0
!--------------------------------------------- !
if ((0.99999 * p(1)) <= pmin) then
... (3 Replies)
Discussion started by: kristinu
3 Replies
LEARN ABOUT LINUX
rbash
RBASH(1) General Commands Manual RBASH(1)NAME
rbash - restricted bash, see bash(1)RESTRICTED SHELL
If bash is started with the name rbash, or the -r option is supplied at invocation, the shell becomes restricted. A restricted shell is
used to set up an environment more controlled than the standard shell. It behaves identically to bash with the exception that the follow-
ing are disallowed or not performed:
o changing directories with cd
o setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV
o specifying command names containing /
o specifying a file name containing a / as an argument to the . builtin command
o specifying a filename containing a slash as an argument to the -p option to the hash builtin command
o importing function definitions from the shell environment at startup
o parsing the value of SHELLOPTS from the shell environment at startup
o redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
o using the exec builtin command to replace the shell with another command
o adding or deleting builtin commands with the -f and -d options to the enable builtin command
o using the enable builtin command to enable disabled shell builtins
o specifying the -p option to the command builtin command
o turning off restricted mode with set +r or set +o restricted.
These restrictions are enforced after any startup files are read.
When a command that is found to be a shell script is executed, rbash turns off any restrictions in the shell spawned to execute the script.
SEE ALSO bash(1)GNU Bash-4.0 2004 Apr 20 RBASH(1)