Styjun

Word for being out at night during curfew

What is the best way for a skeleton to impersonate human without using magic?

How to prevent cooked noodles & dumplings from getting soggy

For the erase-remove idiom, why is the second parameter necessary which points to the end of the container?

Why in a Ethernet LAN, a packet sniffer can obtain all packets sent over the LAN?

Usefulness of complex chord names?

How do I compare the result of "1d20+x, with advantage" to "1d20+y, without advantage", assuming x < y?

What's special about a Bunsen burner?

How to Access data returned from Apex class in JS controller using Lightning web component

How can a Lich look like a human without magic?

Would an 8% reduction in drag outweigh the weight addition from this custom CFD-tested winglet?

Is taking modulus on both sides of an equation valid?

Extrude the faces of a cube symmetrically along XYZ

Create a list of all possible Boolean configurations of three constraints

Does Lawful Interception of 4G / the proposed 5G provide a back door for hackers as well?

Smallest Guaranteed hash collision cycle length

Is it a bad idea to replace pull-up resistors with hard pull-ups?

How can this pool heater gas line be disconnected?

How can I answer high-school writing prompts without sounding weird and fake?

Speculative Biology of a Haplodiploid Humanoid Species

Drawing lines to nearest point

Does the 500 feet falling cap apply per fall, or per turn?

Reaction of borax with NaOH

Who was this character from the Tomb of Annihilation adventure before they became a monster?

Cannot write to file in C program

Improve INSERT-per-second performance of SQLite?Can I ensure that, when fopen()-ing a file for “w”, the program doesn't create a file?Write lines to a text file during program execution - faster wayfprintf not writing to file, despite fclose()C program not writing to text fileWhy I cannot open another file?C - Create/Write/Read named pipeWrite program that pretends to be a TTYfclose(stdout) vs close(STDOUT_FILENO) - CReleasing a file write lock in C?

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty height:90px;width:728px;box-sizing:border-box;

1

I'm trying to write my results to an outputfile, running this C program i Mac Terminal. I have checked that all parts of the program works by writing directly to the terminal, but when I'm trying to write to file, nothing happens.

The "writing to file" line writes on every iteration, however nothing happens to the outputdata.txt file.

I've changed the permissions, and I'm able to write to this file directly from the terminal. However, it doesn't work using the below code.

#define OUTPUTFILE "outputdata.txt"

FILE *ofp;

char ofile_name[50] = OUTPUTFILE;

ofp = fopen(ofile_name, "r");

for (p = 1; p <= NumPattern ; p++) 
 for (k = 1 ; k <= numnodes_out ; k++) 
 fprintf(ofp, "%fn", output_nodes[p][k]);
 fprintf(stdout, "Writing to filen");
 

fclose(ofp);

c

share|improve this question

edited Mar 23 at 12:00

Jonathon Reinhart

93.6k21170240

asked Mar 23 at 11:59

Jonas Hyllseth RyenJonas Hyllseth Ryen

112

add a comment | 

1

I'm trying to write my results to an outputfile, running this C program i Mac Terminal. I have checked that all parts of the program works by writing directly to the terminal, but when I'm trying to write to file, nothing happens.

The "writing to file" line writes on every iteration, however nothing happens to the outputdata.txt file.

I've changed the permissions, and I'm able to write to this file directly from the terminal. However, it doesn't work using the below code.

#define OUTPUTFILE "outputdata.txt"

FILE *ofp;

char ofile_name[50] = OUTPUTFILE;

ofp = fopen(ofile_name, "r");

for (p = 1; p <= NumPattern ; p++) 
 for (k = 1 ; k <= numnodes_out ; k++) 
 fprintf(ofp, "%fn", output_nodes[p][k]);
 fprintf(stdout, "Writing to filen");
 

fclose(ofp);

c

share|improve this question

edited Mar 23 at 12:00

Jonathon Reinhart

93.6k21170240

asked Mar 23 at 11:59

Jonas Hyllseth RyenJonas Hyllseth Ryen

112

add a comment | 

I'm trying to write my results to an outputfile, running this C program i Mac Terminal. I have checked that all parts of the program works by writing directly to the terminal, but when I'm trying to write to file, nothing happens.

The "writing to file" line writes on every iteration, however nothing happens to the outputdata.txt file.

I've changed the permissions, and I'm able to write to this file directly from the terminal. However, it doesn't work using the below code.

#define OUTPUTFILE "outputdata.txt"

FILE *ofp;

char ofile_name[50] = OUTPUTFILE;

ofp = fopen(ofile_name, "r");

for (p = 1; p <= NumPattern ; p++) 
 for (k = 1 ; k <= numnodes_out ; k++) 
 fprintf(ofp, "%fn", output_nodes[p][k]);
 fprintf(stdout, "Writing to filen");
 

fclose(ofp);

c

share|improve this question

edited Mar 23 at 12:00

Jonathon Reinhart

93.6k21170240

asked Mar 23 at 11:59

Jonas Hyllseth RyenJonas Hyllseth Ryen

112

#define OUTPUTFILE "outputdata.txt"

FILE *ofp;

char ofile_name[50] = OUTPUTFILE;

ofp = fopen(ofile_name, "r");

for (p = 1; p <= NumPattern ; p++) 
 for (k = 1 ; k <= numnodes_out ; k++) 
 fprintf(ofp, "%fn", output_nodes[p][k]);
 fprintf(stdout, "Writing to filen");
 

fclose(ofp);

share|improve this question

edited Mar 23 at 12:00

Jonathon Reinhart

93.6k21170240

asked Mar 23 at 11:59

Jonas Hyllseth RyenJonas Hyllseth Ryen

112

share|improve this question

edited Mar 23 at 12:00

Jonathon Reinhart

93.6k21170240

asked Mar 23 at 11:59

Jonas Hyllseth RyenJonas Hyllseth Ryen

112

edited Mar 23 at 12:00

Jonathon Reinhart

93.6k21170240

edited Mar 23 at 12:00

Jonathon Reinhart

93.6k21170240

asked Mar 23 at 11:59

Jonas Hyllseth RyenJonas Hyllseth Ryen

112

asked Mar 23 at 11:59

Jonas Hyllseth RyenJonas Hyllseth Ryen

112

1 Answer
1

active

oldest

votes

4

You're opening the file in read mode, see https://linux.die.net/man/3/fopen.

If you want to write to the file you have to open the file with a mode that supports writing, for example: fopen(ofile_name, "w").

Your primary options if you only want to write to the file are:

1. "w", which will create the file if it does not exist, otherwise it will truncate the file to 0 length (remove everything in the file) and allow you to write to it; or,


2. "a", which will append to the end of an existing file.

Additionally, if you look at the link previously mentioned, you should note that the function could return null if the file does not open successfully. Because of this you should check if the FILE* returned by fopen is not null before operating on it.

#define OUTPUTFILE "outputdata.txt"

FILE *ofp;

char ofile_name[50] = OUTPUTFILE;

ofp = fopen(ofile_name, "r");

if (ofp) 
 for (p = 1; p <= NumPattern ; p++) 
 for (k = 1 ; k <= numnodes_out ; k++) 
 fprintf(ofp, "%fn", output_nodes[p][k]);
 fprintf(stdout, "Writing to filen");
 
 
 fclose(ofp);

share|improve this answer

edited Mar 23 at 12:20

answered Mar 23 at 12:10

JuanJuan

137113

add a comment | 

Your Answer

StackExchange.ifUsing("editor", function ()
StackExchange.using("externalEditor", function ()
StackExchange.using("snippets", function ()
StackExchange.snippets.init();
);
);
, "code-snippets");

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "1"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);



);

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55313502%2fcannot-write-to-file-in-c-program%23new-answer', 'question_page');

);

Post as a guest

Name

Email

Required, but never shown

4

You're opening the file in read mode, see https://linux.die.net/man/3/fopen.

If you want to write to the file you have to open the file with a mode that supports writing, for example: fopen(ofile_name, "w").

Your primary options if you only want to write to the file are:

1. "w", which will create the file if it does not exist, otherwise it will truncate the file to 0 length (remove everything in the file) and allow you to write to it; or,


2. "a", which will append to the end of an existing file.

Additionally, if you look at the link previously mentioned, you should note that the function could return null if the file does not open successfully. Because of this you should check if the FILE* returned by fopen is not null before operating on it.

#define OUTPUTFILE "outputdata.txt"

FILE *ofp;

char ofile_name[50] = OUTPUTFILE;

ofp = fopen(ofile_name, "r");

if (ofp) 
 for (p = 1; p <= NumPattern ; p++) 
 for (k = 1 ; k <= numnodes_out ; k++) 
 fprintf(ofp, "%fn", output_nodes[p][k]);
 fprintf(stdout, "Writing to filen");
 
 
 fclose(ofp);

share|improve this answer

edited Mar 23 at 12:20

answered Mar 23 at 12:10

JuanJuan

137113

add a comment | 

4

You're opening the file in read mode, see https://linux.die.net/man/3/fopen.

If you want to write to the file you have to open the file with a mode that supports writing, for example: fopen(ofile_name, "w").

Your primary options if you only want to write to the file are:

1. "w", which will create the file if it does not exist, otherwise it will truncate the file to 0 length (remove everything in the file) and allow you to write to it; or,


2. "a", which will append to the end of an existing file.

Additionally, if you look at the link previously mentioned, you should note that the function could return null if the file does not open successfully. Because of this you should check if the FILE* returned by fopen is not null before operating on it.

#define OUTPUTFILE "outputdata.txt"

FILE *ofp;

char ofile_name[50] = OUTPUTFILE;

ofp = fopen(ofile_name, "r");

if (ofp) 
 for (p = 1; p <= NumPattern ; p++) 
 for (k = 1 ; k <= numnodes_out ; k++) 
 fprintf(ofp, "%fn", output_nodes[p][k]);
 fprintf(stdout, "Writing to filen");
 
 
 fclose(ofp);

share|improve this answer

edited Mar 23 at 12:20

answered Mar 23 at 12:10

JuanJuan

137113

add a comment | 

You're opening the file in read mode, see https://linux.die.net/man/3/fopen.

If you want to write to the file you have to open the file with a mode that supports writing, for example: fopen(ofile_name, "w").

Your primary options if you only want to write to the file are:

1. "w", which will create the file if it does not exist, otherwise it will truncate the file to 0 length (remove everything in the file) and allow you to write to it; or,


2. "a", which will append to the end of an existing file.

Additionally, if you look at the link previously mentioned, you should note that the function could return null if the file does not open successfully. Because of this you should check if the FILE* returned by fopen is not null before operating on it.

#define OUTPUTFILE "outputdata.txt"

FILE *ofp;

char ofile_name[50] = OUTPUTFILE;

ofp = fopen(ofile_name, "r");

if (ofp) 
 for (p = 1; p <= NumPattern ; p++) 
 for (k = 1 ; k <= numnodes_out ; k++) 
 fprintf(ofp, "%fn", output_nodes[p][k]);
 fprintf(stdout, "Writing to filen");
 
 
 fclose(ofp);

share|improve this answer

edited Mar 23 at 12:20

answered Mar 23 at 12:10

JuanJuan

137113

#define OUTPUTFILE "outputdata.txt"

FILE *ofp;

char ofile_name[50] = OUTPUTFILE;

ofp = fopen(ofile_name, "r");

if (ofp) 
 for (p = 1; p <= NumPattern ; p++) 
 for (k = 1 ; k <= numnodes_out ; k++) 
 fprintf(ofp, "%fn", output_nodes[p][k]);
 fprintf(stdout, "Writing to filen");
 
 
 fclose(ofp);

share|improve this answer

edited Mar 23 at 12:20

answered Mar 23 at 12:10

JuanJuan

137113

answered Mar 23 at 12:10

JuanJuan

137113

answered Mar 23 at 12:10

JuanJuan

137113