I'm implementing a shell in C that supports piping, output redirection, and background processing, and a few other commands. I was wondering how I'd go about implementing the output redirection. So, I'd open a file and I'd fork and execute the command. But how would I get stdout into the file? Any... (10 Replies)
hello all,
i hv attached herewith my program to implement a simple interactive shell in C. no matter hw hard I try, I keep getting some errors. i need help - urgently !!
proj1test7.c: In function `parseCommand':
proj1test7.c:102: warning: assignment makes pointer from integer without a cast... (2 Replies)
Hi,
I am implementing a shell in C, with the following problem...
Suppose the shell is invoked from the command line as
>> myshell < test.in > test.out 2>&1
I have to execute the commands in test.in and redirect them to test.out
How does one detect in the main function that the shell... (1 Reply)
1. The problem statement, all variables and given/known data:
need to implement mkdir, chdir, mv, pwd
given a shell.cpp directory.cpp and some other files
this shell missing these commands, and i need to implement them inside the shell
2. Relevant commands, code, scripts,... (0 Replies)
HI
I want to implement a control mechanism using Shell scripts .The intention is to have controlled number of jobs running in parallel
External process will kickstart 40 jobs in parallel .All the 40 jobs will call the same generic script with different parameter values .But at a... (4 Replies)
Hello,
i'm trying to implement the times() function and i'm programming in C.
I'm using the "struct tms" structure which consists of the fields:
The tms_utime structure member is the CPU time charged for the execution of user instructions of the calling process.
The tms_stime structure... (1 Reply)
I have this code where I have declared a struct with some functions. Trying to write the function implementation outside the struct declaration and do not know how to proceed.
#ifndef ParseEl_hh
#define ParseEl_hh
#include <iostream>
#include <fstream>
#include "DynBaseObj.hh"... (7 Replies)
Hey Guys,
My problem:
I have a script that will be querying the database every minute to see if it gets a response, the response its querying for is "UP" in a table i made called dbup in the database.
Now, I am trying to add the component to implement a timeout if the script does not get a... (2 Replies)
Hello Experts,
Is it possible to implement linked list in shell scripting? is yes then how can we do it? Any working example is highly appreciated.
Thanks in advance. (4 Replies)
I am using DB2 v9 and trying to get country values in comma seperated format using below query
SELECT distinct LISTAGG(COUNTRIES, ',') WITHIN GROUP(ORDER BY EMPLOYEE)
FROM LOCATION ;
Output Achieved
MEXICO,UNITED STATES,INDIA,JAPAN,UNITED KINGDOM,MEXICO,UNITED STATES
The table... (4 Replies)
Discussion started by: Perlbaby
4 Replies
LEARN ABOUT MOJAVE
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)