Programming :: Fetching Return Value From Shell Script?
Jul 12, 2010
from paul's reply in the link (http://www.linuxquestions.org/questi...c-code-181152/) , I am trying to retrieve the count from a shell script using option 1: below is the system call that I have used to call my shell script named "test"
Code:
#include <stdio.h>
#include <stdlib.h>
int main()
{
int i;
i=system("./test 1234");
[Code]...
Here "test" is the shell script that is fetching the count from a table for a particular column("1234") that I am passing as the parameter. When the "test" script alone is run, it is returning the correct count but when trying to check through the C program it's returning some different value. How can I get the exact value from the script in my program above?
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Nov 19, 2009
Is it possible to have an Expect script spawn an SSH session, log in, then go into interactive mode and give control of the SSH session to a Bash script? Here's a simplified example of the script so far:
Code:
#!/bin/bash
expect -c "
[code]....
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Jan 31, 2011
i am using linux for the first time. i have been given a project which will fetch data from csd(comma separated form) and ll display on d screen. i want a c program for linux which ll do the above given task. moreover i want the parameter file(such as location of file, file name,etc..) as a different file. so that i can access this program on any computer.
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May 30, 2011
I'm currently on a Linux machine and the shell prompt is showing me the last return value and number of executed commands (picture included, with these numbers shown in purple).
My own computer doesn't have this, how can I configure it? I'm using Xubunto, if more details are needed let me know -- I'm not much of a Linux user (I don't know what's relevant here).
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Jan 24, 2011
I'm trying to create a super simple shell script, but I cant get a return line. The shell script looks like this (only the part that matters)
Code:
yes '' | ssh-keygen
The idea being it will put in a blank char. Then enter until the program finishes. The problem is, it only does the first time, the next 2 times I have to hit enter, it requires me to input it manually (which is exactly what I'm trying to avoid).
The full script (if you care):
Code:
#!/bin/sh
# Created by Omega
# First, program creates RSA key, named id_rsa and id_rsa.pub
# Second, program send the public code to requsted server.
echo 'Removing old id_rsa key (if applicable)'
rm -rf ~/.ssh/id_rsa.pub
rm -rf ~/.ssh/id_rsa
echo "Creating RSA key"
yes '' | ssh-keygen
# Checking if ssh-kkeygen created requested file
if [ -e ~/.ssh/id_rsa.pub ]
then
echo 'Done'
echo 'Username and Server in: me@server format'
read var1
echo 'Port Number? If standard put 22'
read var2
ssh-copy-id -i ~/.ssh/id_rsa.pub "-p $var2 $var"
else
echo ''
echo 'ERROR, ssh-keygen did not execute correctly'
echo 'Retrying...'
echo ''
echo 'Please leave all options default (just press enter)'
ssh-keygen
if [ -e ~/.ssh/id_rsa.pub ]
then
echo 'Done'
echo 'Username and Server in: me@server format'
read var1
echo 'Port Number? If standard put 22'
read var2
ssh-copy-id -i ~/.ssh/id_rsa.pub "-p $var2 $var1"
else
echo 'ERROR, ssh-keygen did not execute correctly'
echo 'Quitting'
exit
fi
fi
# End
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May 5, 2011
I have a program that I run from the terminal that requires manual input (it's matlab in mex debugging mode, matlab -Dgdb, which starts the GNU C debugger with its own custom settings).
Every time I run this program I always type in the same few commands in the program's interactive shell before I actually start working (for example: run -nojvm; stop at mexFunction; continue). I want to avoid typing these commands and I thought I could do this with shell scripting, saving the commands in the mycommands file, then running: myprogram < mycommands
The problem is that this runs all the commands and then exits the program. I want it to run the commands and return control to me so I can run my commands. Is there a way to tell the shell to use a file or a string as the input to a program then immediately return control to the user without the exiting the program?
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Jun 30, 2010
I trying to write a UART(interfacing of serial devices) to linux machine but after I execute the following code to receive data I need to enter key (carriage return).... but I don't want to remove carriage return/enter key
[Code]....
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Jun 5, 2011
I am trying to create a shell script similar to ls, but which only lists directories. I have the first half working (no argument version), but trying to make it accept an argument, I am failing. My logic is sound I think, but I'm missing something on the syntax.
Code:
if [ $# -eq 0 ] ; then
d=`pwd`
for i in * ; do
if test -d $d/$i ; then
echo "$i:"
code....
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Oct 12, 2010
i am having two small issues with a function i have made.sorry if it is a mess, i am still learning bash.the first is calling the nonpersistssh function (second line) and assigning the return value to nonpersistdiag.the function returns 1, but nonpersistdiag seems to only contain 0. i am unsure on how to proceed.the second problem is the nested else clause on line 10. it is a syntactical error. how would i declare it correctly?
Code: function endsession(){
nonpersistdiag=$[nonpersistssh]# a function that returns an exit code
sudo /etc/init.d/ssh stop; sshdiag=$?
[code]....
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Jun 3, 2011
What are the uses of return 0, return 1 and exit statements in C
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Nov 15, 2010
On this link [URL]4 a return type is defined
Code:
return ((unsigned int)(unsigned long)base & TBASE_DEFERRABLE_FLAG);
What is the above function returning.I am not clear with definition of what is being returned in the above code.
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Jan 18, 2010
I'm confused about what "echo $0" in a shell actually return. Consider these tests:
Code:
[root@e11apvl151 ~]# # Login shell:
[root@e11apvl151 ~]# echo $0
-bash
[root@e11apvl151 ~]# # Starting a new shell
[root@e11apvl151 ~]# bash
[root@e11apvl151 ~]# echo $0
bash
[root@e11apvl151 ~]# screen
[root@e11apvl151 ~]# echo $0
/bin/bash
Depending on wether the shell is a login shell, a regular shell, or a screen utility, I get different results.
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Jun 25, 2010
Is there some type of functional way to read things in the Python shell interpreter similar to less or more in the bash (and other) command line shells?
Example:
Code:
>>> import subprocess
>>> help(subprocess)
...
[pages of stuff to read]
...
I'm hoping so as I hate scrolling and love how less works with simple keystrokes for page-up/page-down/searching etc.
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Mar 15, 2011
I have a file:
979798707
787862348
766428634
I want to see if all the records in the file are present in the contents of the files of a particular directory.
Basically I want to say if grep doesn't return anything, then report.
For example in /tmp dir I have 4 files and flast 2 values (787862348 and 766428634) are present in the files of /tmp dir, but first one (979798707) is not. I want to echo that in a reporting file.
something like:
while read line
do
# if ! grep -rl $line /tmp
echo $line >> are_not_present
done < "myFile"
How do I achieve " if ! grep -rl $line /tmp"? That is, if the line is found by grep, then grep will print the output, but if grep does'nt find it, it will print nothing. How can I check if grep didn't find it (i.e. printed nothing)?
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Dec 16, 2010
I'm reading a text file with fscanf using a loop until feof(inFile). How can I return to the top of the file? As in I have one loop that scans until the eof and then after it there's another loop and I want to start from the beginning of the file again scanning to the end of it. How do I get back there?
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Jan 11, 2010
I am testing the serial ports on a Single Board Computer(SBC) running Linux kernel 2.6.29. I usually do this by connecting the serial port to another PC serial port, then doing "cat /dev/ttyS0" on PC and "echo hello > /dev/ttyS0" on the SBC. However in the current system, "echo hello > /dev/ttyS0" command does not return at all! Also no characters appear on the destination port. I am running the echo command as root. The system boot messages show that the serial port in indeed /dev/ttyS0.
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Mar 10, 2010
I think my title pretty much explains it. I am writing a script and I want to start a program in the background, and when that program finishes I want to check the return value to make sure there was no error.For example normal I would do something like this:
#!/bin/sh
program
if [ ! $? -eq 0 ]; then
echo "There was an error"
exit 1
fi
Now I want to do something like this:
#!/bin/sh
PRTN=`program1 &`
program2
if [ ! $? -eq 0 ]; then
[code]....
In this case if program2 finishes before program1, I don't think the return value from program1 $PRTN would be valid at the time it is checked.
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Aug 5, 2010
I am using pthread_create system call to create a thread. However pthread_create does not return the PID ( process ID). Is there any quick way to fınd the PID of the created thread.
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Mar 19, 2011
C++ code:
Code:
#include<fstream.h>
[code]....
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Mar 10, 2010
I write a little script by bash.
#!/bin/bash
a=`gawk '/Iterations /{print $0}' hoge.log | gawk 'BEGIN{FS=" "}{print ($4)}'`
a=`expr 3 '*' $a`
[code]...
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Jan 25, 2010
I have always encountered this problem in ubuntu bash shell scripts that echo command in a function will be treated as a return value when used in a function. e.g.
[code]...
The output would simply be xyz. Hence the echo seems to function as a "return" command when used in a function with a return value.
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Feb 23, 2010
$val = mkdir $directory, 755
print $val;
does't create directory but return as value '0'
[code]....
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Jun 14, 2010
I have confusion regarding pthreads return value. All in short, is the is a valid return value ?
[source]
void * myThrRoutine(void *arg)
{
struct myStruct **myst = (struct myStruct**) arg;
cout<<"In thread "<<(*myst)->var<<(*myst)->msg<<endl;
int x = 20;
pthread_exit((void*)x);
}
[/source]
This seems to work fine on pthread_join , but I want to ensure it is not by chance.
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Jun 13, 2010
But it's been hell finding an answer, or I just don't know what to look for..I have a prompt that asks for a float, and if the user doesn't put in a valid number, then it should die with an error message.
Code:
def die_with_error():
print 'ERROR: You didn't specify a valid number!'
[code]....
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Jul 9, 2010
I have an a script in /etc/rc.d/init.d script that I would like to start and stop my sample application. I have named my script "foo", then I can start running my application my typing $ foo start but this does not return [OK] like other scripts do and does not return to shell prompt. My application is basically like this
int main()
{
do {
printf("Hi
");
sleep(1);
} while (1);
}
What is missing from my application that prevents from returning the shell prompt?
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Jul 15, 2010
I'm getting some information about C language and this session of a C book (follow the above link) is using a bad example for me. When I'm trying this example of function returning a pointer, my compiler is stating a warning that I return a pointer to a local variable. I realized that it is error prone after all this variable may be override before the function has done his execution. And the author is fooling me saying that this example is "perfectly safe". I'm wrong? There is something that I don't got yet? Sorry but this site is preventing me to post the link of book cause I'm a newbie, so a need the hack it. Just strip out the question signs:
{LINK}
?w?w?w
?cs.cf.ac.uk?
[code]....
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Feb 1, 2010
I have functions which return different data like: int, char*, double...
I also have a list of datatypes (INTEGER, TEXT, REAL...) which can be returned.
I need to map a datatype with function, which purpose is to return it. Therefore, when I determine a datatype, I would like to call the required function without doing switch all the time.
My idea is to have an array of structs like this:
Code:
struct type_func_map
{
int type;
void (*func_wrapper_int)(void); //void (*func_wrapper_text)(void); void (*func_wrapper_real)(void);
};
[Code].....
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Aug 8, 2010
I have a script that reads part of a line, delimited between the first and second intended part by a colon. Then it "chops" the part after the colon, which are words offset by commas (counting them beforehand so as to catch every word in the string's second part), like this:
Code:
"COLORS.JPG:red,orange,yellow,green,"
(Returning)
red
[code]....
single script that parses/breaks both parts of a line like this "COLORS.JPG:red,orange,yellow,green;blue,indigo,violet," so that the two parts, separated into single words (or two and three words, sometimes with spaces) can be used as single-line annotations and written to JPEG files using Exiv2. So far, I haven't been able to come up with a script that does this without one part of the total string(usually that part after the colon) becoming the first word in the second array. In other words, I look for this:
KEYWORDS:
[ ]red
[ ]orange
[ ]yellow
[code]....
Or vice-versa (ie, the second array winds up as a single-line "member" of the first). I think it's because I'm using a single while read loop to read the text file in which the filenames and substrings happen to be. If there's some way of reading a file once and going back to the beginning to read it again in another while loop, I haven't found it.
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Oct 30, 2010
I have a function that returns a boolean value, True of False. Is there any convention whether 0 = False or 0 = True? It should be obvious, 0=False, 1=True. However programs usually return 0 on success and reserve higher numbers for error values. I.e. if the program finishes successfully (function int main() finishes successfully ), it returns 0 - and that contradicts that 0 should be false.
And especially if I want a function to do some computations on parameters passed by reference and return success status. Should it return 1 (true) for success, or should it return 0 for success - like any Unix program does?
Is there any convention for this?
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Oct 21, 2010
I'm witting a piece of code that needs to read key presses. However I cannot use them as stream, but rather need discrete reads. The code is to simulate an io board interface. So When I press say "d" I need to read it in instantly, not wait for return. I've tried sdl, but no luck (I'm reading in a thread and it causes some problems) I'm using linux so can't use conio.h functions, I've tired gatch from cureses but this still waits for return.So in C/c++ is there a way I can read instant key presses.
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