I am reading a file and copying selected lines from the file into another using echo.
For eg:
while read line
do
if ((some logic to determine whether I need to copy the current line to another file))
then
echo $line > tempfile
fi
done<srcfile
The problem I have is the data in the file... (1 Reply)
Hi,
How can I avoid multiple 'cat while read ....? in my script.
In my script, I am taking the inputs from the temp text file and doing the
(
cat while read input
do
...
...
done
)
task and deleting later.
I know it'll raise the perfomance issue. How to avoid this? (2 Replies)
Hi Guys.
I have 3 variables
$HOST
$Username
$Password
I want to connect to a remote server using SFTP.
usr/bin/sftp -o Cipher=blowfish $HostWhere do I put in the options for the username and pwd??? I have tried different ways and nothing works. It keeps coming back and promting me.
... (5 Replies)
Sometimes we need a single instance of a script to run at a time. Meaning, the script itself should detects whether any instances of himself are still running and act accordingly.
When multiple instances of one script running, it’s easy to cause problems. I’ve ever seen that about 350 instances... (4 Replies)
I have a script that collects data from about 200 servers using 'ssh'. The problem is that, process sometime hangs at some point stopping the execution of the script. Please give me some idea how can I force the execution to jump to the next step if there arises any problem !! Thanks for replies if... (1 Reply)
consider the small piece of code
while read line
do
echo $line
done < example
content of example file
sadasdasdasdsa erwerewrwr ergdgdfgf rgerg erwererwr
the output is like
sadasdasdasdsa erwerewrwr ergdgdfgf rgerg erwererwr
the... (4 Replies)
Hello,
I am trying to run some code on Matlab over ssh . The code takes around 5-6 hours to complete. so after giving the command to run it , I locked my machine and then went off to sleep at night, only to discover in the morning that I get this message :
...Code running, partial results... (1 Reply)
Hello,
I have currently coded a bash script below in which it does the following:
# Archives compressed file from another location.
Basically it moves *.gz files to another location.
The script also sends an email whenever a new compressed file is placed. This is the issue that i... (5 Replies)
Hi,
I want to validate ssh connection one after one for multiple servers..... password less keys already setup but now i want to validate if ssh is working fine or not...
I have .sh script like below and i have servers.txt contains all the list of servers
#/bin/bash
for host in $(cat... (3 Replies)
Discussion started by: sreeram4
3 Replies
LEARN ABOUT CENTOS
subst
subst(n) Tcl Built-In Commands subst(n)
__________________________________________________________________________________________________________________________________________________NAME
subst - Perform backslash, command, and variable substitutions
SYNOPSIS
subst ?-nobackslashes? ?-nocommands? ?-novariables? string
_________________________________________________________________DESCRIPTION
This command performs variable substitutions, command substitutions, and backslash substitutions on its string argument and returns the
fully-substituted result. The substitutions are performed in exactly the same way as for Tcl commands. As a result, the string argument
is actually substituted twice, once by the Tcl parser in the usual fashion for Tcl commands, and again by the subst command.
If any of the -nobackslashes, -nocommands, or -novariables are specified, then the corresponding substitutions are not performed. For
example, if -nocommands is specified, command substitution is not performed: open and close brackets are treated as ordinary characters
with no special interpretation.
Note that the substitution of one kind can include substitution of other kinds. For example, even when the -novariables option is speci-
fied, command substitution is performed without restriction. This means that any variable substitution necessary to complete the command
substitution will still take place. Likewise, any command substitution necessary to complete a variable substitution will take place, even
when -nocommands is specified. See the EXAMPLES below.
If an error occurs during substitution, then subst will return that error. If a break exception occurs during command or variable substi-
tution, the result of the whole substitution will be the string (as substituted) up to the start of the substitution that raised the excep-
tion. If a continue exception occurs during the evaluation of a command or variable substitution, an empty string will be substituted for
that entire command or variable substitution (as long as it is well-formed Tcl.) If a return exception occurs, or any other return code is
returned during command or variable substitution, then the returned value is substituted for that substitution. See the EXAMPLES below.
In this way, all exceptional return codes are "caught" by subst. The subst command itself will either return an error, or will complete
successfully.
EXAMPLES
When it performs its substitutions, subst does not give any special treatment to double quotes or curly braces (except within command sub-
stitutions) so the script
set a 44
subst {xyz {$a}}
returns "xyz {44}", not "xyz {$a}" and the script
set a "p} q {r"
subst {xyz {$a}}
returns "xyz {p} q {r}", not "xyz {p} q {r}".
When command substitution is performed, it includes any variable substitution necessary to evaluate the script.
set a 44
subst -novariables {$a [format $a]}
returns "$a 44", not "$a $a". Similarly, when variable substitution is performed, it includes any command substitution necessary to
retrieve the value of the variable.
proc b {} {return c}
array set a {c c [b] tricky}
subst -nocommands {[b] $a([b])}
returns "[b] c", not "[b] tricky".
The continue and break exceptions allow command substitutions to prevent substitution of the rest of the command substitution and the rest
of string respectively, giving script authors more options when processing text using subst. For example, the script
subst {abc,[break],def}
returns "abc,", not "abc,,def" and the script
subst {abc,[continue;expr {1+2}],def}
returns "abc,,def", not "abc,3,def".
Other exceptional return codes substitute the returned value
subst {abc,[return foo;expr {1+2}],def}
returns "abc,foo,def", not "abc,3,def" and
subst {abc,[return -code 10 foo;expr {1+2}],def}
also returns "abc,foo,def", not "abc,3,def".
SEE ALSO
Tcl(n), eval(n), break(n), continue(n)
KEYWORDS
backslash substitution, command substitution, variable substitution
Tcl 7.4 subst(n)