How to read a line from the console in C

Question

What is the simplest way to read a full line in a C console program The text entered might have a variable length and we can t make any assumption about its content

User · Answer

A very simple but unsafe implementation to read line for static allocation:

char line[1024];

scanf("%[^\n]", line);

A safer implementation, without the possibility of buffer overflow, but with the possibility of not reading the whole line, is:

char line[1024];

scanf("%1023[^\n]", line);

Not the 'difference by one' between the length specified declaring the variable and the length specified in the format string. It is a historical artefact.

User · Answer

The best and simplest way to read a line from a console is using the getchar   function  whereby you will store one character at a time in an array     char message N             character array for the message  you can always change the character length    int i   0              loop counter     printf   Enter a message       message i    getchar          get the first character    while  message i       n         message   i    getchar       gets the next character       printf   Entered message is      for  i   0  i  lt  N  i         printf    c   message i      return   0

User · Answer

As suggested  you can use getchar   to read from the console until an end-of-line or an EOF is returned  building your own buffer   Growing buffer dynamically can occur if you are unable to set a reasonable maximum line size   You can use also use fgets as a safe way to obtain a line as a C null-terminated string    include  lt stdio h gt   char line 1024       Generously large value for most situations     char  eof   line 0      0      Ensure empty line if no input delivered    line sizeof line -1       0       Ensure no false-null at end of buffer     eof   fgets line  sizeof line   stdin     If you have exhausted the console input or if the operation failed for some reason  eof    NULL is returned and the line buffer might be unchanged  which is why setting the first char to   0  is handy    fgets will not overfill line   and it will ensure that there is a null after the last-accepted character on a successful return   If end-of-line was reached  the character preceding the terminating   0  will be a   n    If there is no terminating   n  before the ending   0  it may be that there is more data or that the next request will report end-of-file   You ll have to do another fgets to determine which is which    In this regard  looping with getchar   is easier    In the  updated  example code above  if line sizeof line -1       0  after successful fgets  you know that the buffer was filled completely   If that position is proceeded by a   n  you know you were lucky   Otherwise  there is either more data or an end-of-file up ahead in stdin    When the buffer is not filled completely  you could still be at an end-of-file and there also might not be a   n  at the end of the current line   Since you have to scan the string to find and or eliminate any   n  before the end of the string  the first   0  in the buffer   I am inclined to prefer using getchar   in the first place    Do what you need to do to deal with there still being more line than the amount you read as the first chunk   The examples of dynamically-growing a buffer can be made to work with either getchar or fgets   There are some tricky edge cases to watch out for  like remembering to have the next input start storing at the position of the   0  that ended the previous input before the buffer was extended

User · Answer

So  if you were looking for command arguments  take a look at Tim s answer  If you just want to read a line from console    include  lt stdio h gt   int main       char string  256     printf   Insert your full address        gets  string     printf   Your address is   s n  string     return 0      Yes  it is not secure  you can do buffer overrun  it does not check for end of file  it does not support encodings and a lot of other stuff  Actually I didn t even think whether it did ANY of this stuff   I agree I kinda screwed up    But   when I see a question like  How to read a line from the console in C    I assume a person needs something simple  like gets   and not 100 lines of code like above  Actually  I think  if you try to write those 100 lines of code in reality  you would do many more mistakes  than you would have done had you chosen gets

User · Answer

You need dynamic memory management  and use the fgets function to read your line  However  there seems to be no way to see how many characters it read  So you use fgetc   char   getline void        char   line   malloc 100     linep   line      size t lenmax   100  len   lenmax      int c       if line    NULL          return NULL       for               c   fgetc stdin           if c    EOF              break           if --len    0                len   lenmax              char   linen   realloc linep  lenmax    2                if linen    NULL                    free linep                   return NULL                            line   linen    line - linep               linep   linen                     if   line     c       n               break             line     0       return linep      Note  Never use gets   It does not do bounds checking and can overflow your buffer

User · Answer

This function should do what you want   char  readLine  FILE  file       char buffer 1024    char  result   0   int length   0    while   feof file          fgets  buffer  sizeof buffer   file      int len   strlen buffer     buffer len    0     length    len    char  tmp    char  malloc length 1     tmp 0    0     if  result           strcpy  tmp  result       free  result       result   tmp          strcat  result  buffer       if  strstr  buffer    n    break        return result      char  line   readLine  stdin       Use it    free  line      I hope this helps

User · Answer

getline runnable example getline was mentioned on this answer but here is an example  It is POSIX 7  allocates memory for us  and reuses the allocated buffer on a loop nicely  Pointer newbs  read this  Why is the first argument of getline a pointer to pointer  quot char   quot  instead of  quot char  quot   main c  define  XOPEN SOURCE 700  include  lt stdio h gt   include  lt stdlib h gt   int main void        char  line   NULL      size t len   0      ssize t read   0      while  1            puts  quot enter a line quot            read   getline  amp line   amp len  stdin           if  read    -1              break          printf  quot line    s quot   line           printf  quot line length    zu n quot   read           puts  quot  quot              free line       return 0     Compile and run  gcc -ggdb3 -O0 -std c99 -Wall -Wextra -pedantic -o main out main c   main out  Outcome  this shows on therminal  enter a line  Then if you type  asdf  and press enter  this shows up  line   asdf line length   5  followed by another  enter a line  Or from a pipe to stdin  printf  asdf nqwer n      main out  gives  enter a line line   asdf line length   5  enter a line line   qwer line length   5  enter a line  Tested on Ubuntu 20 04  glibc implementation No POSIX  Maybe you want to look at the glibc 2 23 implementation  It resolves to getdelim  which is a simple POSIX superset of getline with an arbitrary line terminator  It doubles the allocated memory whenever increase is needed  and looks thread-safe  It requires some macro expansion  but you re unlikely to do much better

User · Answer

This function should do what you want   char  readLine  FILE  file       char buffer 1024    char  result   0   int length   0    while   feof file          fgets  buffer  sizeof buffer   file      int len   strlen buffer     buffer len    0     length    len    char  tmp    char  malloc length 1     tmp 0    0     if  result           strcpy  tmp  result       free  result       result   tmp          strcat  result  buffer       if  strstr  buffer    n    break        return result      char  line   readLine  stdin       Use it    free  line      I hope this helps

User · Answer

As suggested  you can use getchar   to read from the console until an end-of-line or an EOF is returned  building your own buffer   Growing buffer dynamically can occur if you are unable to set a reasonable maximum line size   You can use also use fgets as a safe way to obtain a line as a C null-terminated string    include  lt stdio h gt   char line 1024       Generously large value for most situations     char  eof   line 0      0      Ensure empty line if no input delivered    line sizeof line -1       0       Ensure no false-null at end of buffer     eof   fgets line  sizeof line   stdin     If you have exhausted the console input or if the operation failed for some reason  eof    NULL is returned and the line buffer might be unchanged  which is why setting the first char to   0  is handy    fgets will not overfill line   and it will ensure that there is a null after the last-accepted character on a successful return   If end-of-line was reached  the character preceding the terminating   0  will be a   n    If there is no terminating   n  before the ending   0  it may be that there is more data or that the next request will report end-of-file   You ll have to do another fgets to determine which is which    In this regard  looping with getchar   is easier    In the  updated  example code above  if line sizeof line -1       0  after successful fgets  you know that the buffer was filled completely   If that position is proceeded by a   n  you know you were lucky   Otherwise  there is either more data or an end-of-file up ahead in stdin    When the buffer is not filled completely  you could still be at an end-of-file and there also might not be a   n  at the end of the current line   Since you have to scan the string to find and or eliminate any   n  before the end of the string  the first   0  in the buffer   I am inclined to prefer using getchar   in the first place    Do what you need to do to deal with there still being more line than the amount you read as the first chunk   The examples of dynamically-growing a buffer can be made to work with either getchar or fgets   There are some tricky edge cases to watch out for  like remembering to have the next input start storing at the position of the   0  that ended the previous input before the buffer was extended

User · Answer

If you are using the GNU C library or another POSIX-compliant library  you can use getline   and pass stdin to it for the file stream

User · Answer

So  if you were looking for command arguments  take a look at Tim s answer  If you just want to read a line from console    include  lt stdio h gt   int main       char string  256     printf   Insert your full address        gets  string     printf   Your address is   s n  string     return 0      Yes  it is not secure  you can do buffer overrun  it does not check for end of file  it does not support encodings and a lot of other stuff  Actually I didn t even think whether it did ANY of this stuff   I agree I kinda screwed up    But   when I see a question like  How to read a line from the console in C    I assume a person needs something simple  like gets   and not 100 lines of code like above  Actually  I think  if you try to write those 100 lines of code in reality  you would do many more mistakes  than you would have done had you chosen gets

User · Answer

I came across the same problem some time ago  this was my solutuion  hope it helps         Initial size of the read buffer      define DEFAULT BUFFER 1024        Standard boolean type definition     typedef enum  false   0  true   1  bool         Flags errors in pointer returning functions     bool has err   false         Reads the next line of text from file and returns it     The line must be free  d afterwards        This function will segfault on binary data      char  readLine FILE  file       char  buffer     NULL      char  tmp buf    NULL      bool line read   false      int  iteration   0      int  offset      0       if file    NULL           fprintf stderr   readLine  NULL file pointer passed  n            has err   true           return NULL             while  line read           if  tmp buf   malloc DEFAULT BUFFER      NULL               fprintf stderr   readLine  Unable to allocate temporary buffer  n                if buffer    NULL                  free buffer               has err   true               return NULL                     if fgets tmp buf  DEFAULT BUFFER  file     NULL               free tmp buf                break                     if tmp buf strlen tmp buf  - 1       n      we have an end of line                line read   true           offset   DEFAULT BUFFER    iteration   1            if  buffer   realloc buffer  offset      NULL               fprintf stderr   readLine  Unable to reallocate buffer  n                free tmp buf               has err   true               return NULL                     offset   DEFAULT BUFFER   iteration - iteration           if memcpy buffer   offset  tmp buf  DEFAULT BUFFER     NULL               fprintf stderr   readLine  Cannot copy to buffer n                free tmp buf               if buffer    NULL                  free buffer               has err   true               return NULL                     free tmp buf           iteration               return buffer

User · Answer

You need dynamic memory management  and use the fgets function to read your line  However  there seems to be no way to see how many characters it read  So you use fgetc   char   getline void        char   line   malloc 100     linep   line      size t lenmax   100  len   lenmax      int c       if line    NULL          return NULL       for               c   fgetc stdin           if c    EOF              break           if --len    0                len   lenmax              char   linen   realloc linep  lenmax    2                if linen    NULL                    free linep                   return NULL                            line   linen    line - linep               linep   linen                     if   line     c       n               break             line     0       return linep      Note  Never use gets   It does not do bounds checking and can overflow your buffer

User · Answer

I came across the same problem some time ago  this was my solutuion  hope it helps         Initial size of the read buffer      define DEFAULT BUFFER 1024        Standard boolean type definition     typedef enum  false   0  true   1  bool         Flags errors in pointer returning functions     bool has err   false         Reads the next line of text from file and returns it     The line must be free  d afterwards        This function will segfault on binary data      char  readLine FILE  file       char  buffer     NULL      char  tmp buf    NULL      bool line read   false      int  iteration   0      int  offset      0       if file    NULL           fprintf stderr   readLine  NULL file pointer passed  n            has err   true           return NULL             while  line read           if  tmp buf   malloc DEFAULT BUFFER      NULL               fprintf stderr   readLine  Unable to allocate temporary buffer  n                if buffer    NULL                  free buffer               has err   true               return NULL                     if fgets tmp buf  DEFAULT BUFFER  file     NULL               free tmp buf                break                     if tmp buf strlen tmp buf  - 1       n      we have an end of line                line read   true           offset   DEFAULT BUFFER    iteration   1            if  buffer   realloc buffer  offset      NULL               fprintf stderr   readLine  Unable to reallocate buffer  n                free tmp buf               has err   true               return NULL                     offset   DEFAULT BUFFER   iteration - iteration           if memcpy buffer   offset  tmp buf  DEFAULT BUFFER     NULL               fprintf stderr   readLine  Cannot copy to buffer n                free tmp buf               if buffer    NULL                  free buffer               has err   true               return NULL                     free tmp buf           iteration               return buffer

User · Answer

How to read a line from the console in C    Building your own function  is one of the ways that would help you to achieve reading a line from console  I m using dynamic memory allocation to allocate the required amount of memory required  When we are about to exhaust the allocated memory  we try to double the size of memory  And here I m using a loop to scan each character of the string one by one using the getchar   function until the user enters   n  or EOF character  finally we remove any additionally allocated memory before returning the line     the function to read lines of variable length  char  scan line char  line        int ch                 as getchar   returns  int      long capacity   0      capacity of the buffer     long length   0        maintains the length of the string     char  temp   NULL      use additional pointer to perform allocations in order to avoid memory leaks      while     ch   getchar         n    amp  amp   ch    EOF                  if  length   1   gt   capacity                           resetting capacity             if  capacity    0                  capacity   2     some initial fixed length              else                 capacity    2     double the size                 try reallocating the memory             if   temp   realloc line  capacity   sizeof char       NULL     allocating memory                               printf  quot ERROR  unsuccessful allocation quot                       return line  or you can exit                 exit 1                              line   temp                     line length     char  ch    type casting  int  to  char          length              line length   1      0     inserting null character at the end         remove additionally allocated memory     if   temp   realloc line   length   1    sizeof char       NULL                 printf  quot ERROR  unsuccessful allocation quot               return line  or you can exit         exit 1              line   temp      return line      Now you could read a full line this way    char  line   NULL   line   scan line line       Here s an example program using the scan line   function    include  lt stdio h gt   include  lt stdlib h gt    for dynamic allocation functions  char  scan line char  line                      int main void        char  a   NULL       a   scan line a     function call to scan the line      printf  quot  s n quot  a     printing the scanned line      free a     don t forget to free the malloc d pointer    sample input   Twinkle Twinkle little star     in the sky   sample output   Twinkle Twinkle little star     in the sky

User · Answer

A very simple but unsafe implementation to read line for static allocation:

char line[1024];

scanf("%[^\n]", line);

A safer implementation, without the possibility of buffer overflow, but with the possibility of not reading the whole line, is:

char line[1024];

scanf("%1023[^\n]", line);

Not the 'difference by one' between the length specified declaring the variable and the length specified in the format string. It is a historical artefact.

User · Answer

Something like this   unsigned int getConsoleInput char   pStrBfr    pass in pointer to char pointer  returns size of buffer       char   strbfr      int c      unsigned int i      i   0      strbfr    char  malloc sizeof char        if strbfr  NULL  goto error      while   c   getchar         n   amp  amp  c    EOF                 strbfr i     char c          i            strbfr    void  realloc  void  strbfr sizeof char   i 1              on realloc error  NULL is returned but original buffer is unchanged           NOTE  the buffer WILL NOT be NULL terminated since last           chracter came from console         if strbfr  NULL  goto error            strbfr i      0        pStrBfr   strbfr    successfully returns pointer to NULL terminated buffer     return i   1       error       pStrBfr   strbfr      return i   1

User · Answer

You might need to use a character by character  getc    loop to ensure you have no buffer overflows and don t truncate the input

User · Answer

I came across the same problem some time ago  this was my solutuion  hope it helps         Initial size of the read buffer      define DEFAULT BUFFER 1024        Standard boolean type definition     typedef enum  false   0  true   1  bool         Flags errors in pointer returning functions     bool has err   false         Reads the next line of text from file and returns it     The line must be free  d afterwards        This function will segfault on binary data      char  readLine FILE  file       char  buffer     NULL      char  tmp buf    NULL      bool line read   false      int  iteration   0      int  offset      0       if file    NULL           fprintf stderr   readLine  NULL file pointer passed  n            has err   true           return NULL             while  line read           if  tmp buf   malloc DEFAULT BUFFER      NULL               fprintf stderr   readLine  Unable to allocate temporary buffer  n                if buffer    NULL                  free buffer               has err   true               return NULL                     if fgets tmp buf  DEFAULT BUFFER  file     NULL               free tmp buf                break                     if tmp buf strlen tmp buf  - 1       n      we have an end of line                line read   true           offset   DEFAULT BUFFER    iteration   1            if  buffer   realloc buffer  offset      NULL               fprintf stderr   readLine  Unable to reallocate buffer  n                free tmp buf               has err   true               return NULL                     offset   DEFAULT BUFFER   iteration - iteration           if memcpy buffer   offset  tmp buf  DEFAULT BUFFER     NULL               fprintf stderr   readLine  Cannot copy to buffer n                free tmp buf               if buffer    NULL                  free buffer               has err   true               return NULL                     free tmp buf           iteration               return buffer

User · Answer

If you are using the GNU C library or another POSIX-compliant library  you can use getline   and pass stdin to it for the file stream

User · Answer

As suggested  you can use getchar   to read from the console until an end-of-line or an EOF is returned  building your own buffer   Growing buffer dynamically can occur if you are unable to set a reasonable maximum line size   You can use also use fgets as a safe way to obtain a line as a C null-terminated string    include  lt stdio h gt   char line 1024       Generously large value for most situations     char  eof   line 0      0      Ensure empty line if no input delivered    line sizeof line -1       0       Ensure no false-null at end of buffer     eof   fgets line  sizeof line   stdin     If you have exhausted the console input or if the operation failed for some reason  eof    NULL is returned and the line buffer might be unchanged  which is why setting the first char to   0  is handy    fgets will not overfill line   and it will ensure that there is a null after the last-accepted character on a successful return   If end-of-line was reached  the character preceding the terminating   0  will be a   n    If there is no terminating   n  before the ending   0  it may be that there is more data or that the next request will report end-of-file   You ll have to do another fgets to determine which is which    In this regard  looping with getchar   is easier    In the  updated  example code above  if line sizeof line -1       0  after successful fgets  you know that the buffer was filled completely   If that position is proceeded by a   n  you know you were lucky   Otherwise  there is either more data or an end-of-file up ahead in stdin    When the buffer is not filled completely  you could still be at an end-of-file and there also might not be a   n  at the end of the current line   Since you have to scan the string to find and or eliminate any   n  before the end of the string  the first   0  in the buffer   I am inclined to prefer using getchar   in the first place    Do what you need to do to deal with there still being more line than the amount you read as the first chunk   The examples of dynamically-growing a buffer can be made to work with either getchar or fgets   There are some tricky edge cases to watch out for  like remembering to have the next input start storing at the position of the   0  that ended the previous input before the buffer was extended

User · Answer

As suggested  you can use getchar   to read from the console until an end-of-line or an EOF is returned  building your own buffer   Growing buffer dynamically can occur if you are unable to set a reasonable maximum line size   You can use also use fgets as a safe way to obtain a line as a C null-terminated string    include  lt stdio h gt   char line 1024       Generously large value for most situations     char  eof   line 0      0      Ensure empty line if no input delivered    line sizeof line -1       0       Ensure no false-null at end of buffer     eof   fgets line  sizeof line   stdin     If you have exhausted the console input or if the operation failed for some reason  eof    NULL is returned and the line buffer might be unchanged  which is why setting the first char to   0  is handy    fgets will not overfill line   and it will ensure that there is a null after the last-accepted character on a successful return   If end-of-line was reached  the character preceding the terminating   0  will be a   n    If there is no terminating   n  before the ending   0  it may be that there is more data or that the next request will report end-of-file   You ll have to do another fgets to determine which is which    In this regard  looping with getchar   is easier    In the  updated  example code above  if line sizeof line -1       0  after successful fgets  you know that the buffer was filled completely   If that position is proceeded by a   n  you know you were lucky   Otherwise  there is either more data or an end-of-file up ahead in stdin    When the buffer is not filled completely  you could still be at an end-of-file and there also might not be a   n  at the end of the current line   Since you have to scan the string to find and or eliminate any   n  before the end of the string  the first   0  in the buffer   I am inclined to prefer using getchar   in the first place    Do what you need to do to deal with there still being more line than the amount you read as the first chunk   The examples of dynamically-growing a buffer can be made to work with either getchar or fgets   There are some tricky edge cases to watch out for  like remembering to have the next input start storing at the position of the   0  that ended the previous input before the buffer was extended

User · Answer

Something like this   unsigned int getConsoleInput char   pStrBfr    pass in pointer to char pointer  returns size of buffer       char   strbfr      int c      unsigned int i      i   0      strbfr    char  malloc sizeof char        if strbfr  NULL  goto error      while   c   getchar         n   amp  amp  c    EOF                 strbfr i     char c          i            strbfr    void  realloc  void  strbfr sizeof char   i 1              on realloc error  NULL is returned but original buffer is unchanged           NOTE  the buffer WILL NOT be NULL terminated since last           chracter came from console         if strbfr  NULL  goto error            strbfr i      0        pStrBfr   strbfr    successfully returns pointer to NULL terminated buffer     return i   1       error       pStrBfr   strbfr      return i   1

User · Answer

This function should do what you want   char  readLine  FILE  file       char buffer 1024    char  result   0   int length   0    while   feof file          fgets  buffer  sizeof buffer   file      int len   strlen buffer     buffer len    0     length    len    char  tmp    char  malloc length 1     tmp 0    0     if  result           strcpy  tmp  result       free  result       result   tmp          strcat  result  buffer       if  strstr  buffer    n    break        return result      char  line   readLine  stdin       Use it    free  line      I hope this helps

User · Answer

I came across the same problem some time ago  this was my solutuion  hope it helps         Initial size of the read buffer      define DEFAULT BUFFER 1024        Standard boolean type definition     typedef enum  false   0  true   1  bool         Flags errors in pointer returning functions     bool has err   false         Reads the next line of text from file and returns it     The line must be free  d afterwards        This function will segfault on binary data      char  readLine FILE  file       char  buffer     NULL      char  tmp buf    NULL      bool line read   false      int  iteration   0      int  offset      0       if file    NULL           fprintf stderr   readLine  NULL file pointer passed  n            has err   true           return NULL             while  line read           if  tmp buf   malloc DEFAULT BUFFER      NULL               fprintf stderr   readLine  Unable to allocate temporary buffer  n                if buffer    NULL                  free buffer               has err   true               return NULL                     if fgets tmp buf  DEFAULT BUFFER  file     NULL               free tmp buf                break                     if tmp buf strlen tmp buf  - 1       n      we have an end of line                line read   true           offset   DEFAULT BUFFER    iteration   1            if  buffer   realloc buffer  offset      NULL               fprintf stderr   readLine  Unable to reallocate buffer  n                free tmp buf               has err   true               return NULL                     offset   DEFAULT BUFFER   iteration - iteration           if memcpy buffer   offset  tmp buf  DEFAULT BUFFER     NULL               fprintf stderr   readLine  Cannot copy to buffer n                free tmp buf               if buffer    NULL                  free buffer               has err   true               return NULL                     free tmp buf           iteration               return buffer

User · Answer

You might need to use a character by character  getc    loop to ensure you have no buffer overflows and don t truncate the input

User · Answer

If you are using the GNU C library or another POSIX-compliant library  you can use getline   and pass stdin to it for the file stream

User · Answer

getline runnable example getline was mentioned on this answer but here is an example  It is POSIX 7  allocates memory for us  and reuses the allocated buffer on a loop nicely  Pointer newbs  read this  Why is the first argument of getline a pointer to pointer  quot char   quot  instead of  quot char  quot   main c  define  XOPEN SOURCE 700  include  lt stdio h gt   include  lt stdlib h gt   int main void        char  line   NULL      size t len   0      ssize t read   0      while  1            puts  quot enter a line quot            read   getline  amp line   amp len  stdin           if  read    -1              break          printf  quot line    s quot   line           printf  quot line length    zu n quot   read           puts  quot  quot              free line       return 0     Compile and run  gcc -ggdb3 -O0 -std c99 -Wall -Wextra -pedantic -o main out main c   main out  Outcome  this shows on therminal  enter a line  Then if you type  asdf  and press enter  this shows up  line   asdf line length   5  followed by another  enter a line  Or from a pipe to stdin  printf  asdf nqwer n      main out  gives  enter a line line   asdf line length   5  enter a line line   qwer line length   5  enter a line  Tested on Ubuntu 20 04  glibc implementation No POSIX  Maybe you want to look at the glibc 2 23 implementation  It resolves to getdelim  which is a simple POSIX superset of getline with an arbitrary line terminator  It doubles the allocated memory whenever increase is needed  and looks thread-safe  It requires some macro expansion  but you re unlikely to do much better

User · Answer

The best and simplest way to read a line from a console is using the getchar   function  whereby you will store one character at a time in an array     char message N             character array for the message  you can always change the character length    int i   0              loop counter     printf   Enter a message       message i    getchar          get the first character    while  message i       n         message   i    getchar       gets the next character       printf   Entered message is      for  i   0  i  lt  N  i         printf    c   message i      return   0

User · Answer

You might need to use a character by character  getc    loop to ensure you have no buffer overflows and don t truncate the input

User · Answer

A very simple but unsafe implementation to read line for static allocation:

char line[1024];

scanf("%[^\n]", line);

A safer implementation, without the possibility of buffer overflow, but with the possibility of not reading the whole line, is:

char line[1024];

scanf("%1023[^\n]", line);

Not the 'difference by one' between the length specified declaring the variable and the length specified in the format string. It is a historical artefact.

User · Answer

On BSD systems and Android you can also use fgetln    include  lt stdio h gt   char   fgetln FILE  stream  size t  len     Like so   size t line len  const char  line   fgetln stdin   amp line len     The line is not null terminated and contains  n  or whatever your platform is using  in the end  It becomes invalid after the next I O operation on stream

User · Answer

A very simple but unsafe implementation to read line for static allocation:

char line[1024];

scanf("%[^\n]", line);

A safer implementation, without the possibility of buffer overflow, but with the possibility of not reading the whole line, is:

char line[1024];

scanf("%1023[^\n]", line);

Not the 'difference by one' between the length specified declaring the variable and the length specified in the format string. It is a historical artefact.

User · Answer

So  if you were looking for command arguments  take a look at Tim s answer  If you just want to read a line from console    include  lt stdio h gt   int main       char string  256     printf   Insert your full address        gets  string     printf   Your address is   s n  string     return 0      Yes  it is not secure  you can do buffer overrun  it does not check for end of file  it does not support encodings and a lot of other stuff  Actually I didn t even think whether it did ANY of this stuff   I agree I kinda screwed up    But   when I see a question like  How to read a line from the console in C    I assume a person needs something simple  like gets   and not 100 lines of code like above  Actually  I think  if you try to write those 100 lines of code in reality  you would do many more mistakes  than you would have done had you chosen gets

User · Answer

You might need to use a character by character  getc    loop to ensure you have no buffer overflows and don t truncate the input

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You need dynamic memory management  and use the fgets function to read your line  However  there seems to be no way to see how many characters it read  So you use fgetc   char   getline void        char   line   malloc 100     linep   line      size t lenmax   100  len   lenmax      int c       if line    NULL          return NULL       for               c   fgetc stdin           if c    EOF              break           if --len    0                len   lenmax              char   linen   realloc linep  lenmax    2                if linen    NULL                    free linep                   return NULL                            line   linen    line - linep               linep   linen                     if   line     c       n               break             line     0       return linep      Note  Never use gets   It does not do bounds checking and can overflow your buffer

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This function should do what you want   char  readLine  FILE  file       char buffer 1024    char  result   0   int length   0    while   feof file          fgets  buffer  sizeof buffer   file      int len   strlen buffer     buffer len    0     length    len    char  tmp    char  malloc length 1     tmp 0    0     if  result           strcpy  tmp  result       free  result       result   tmp          strcat  result  buffer       if  strstr  buffer    n    break        return result      char  line   readLine  stdin       Use it    free  line      I hope this helps

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How to read a line from the console in C    Building your own function  is one of the ways that would help you to achieve reading a line from console  I m using dynamic memory allocation to allocate the required amount of memory required  When we are about to exhaust the allocated memory  we try to double the size of memory  And here I m using a loop to scan each character of the string one by one using the getchar   function until the user enters   n  or EOF character  finally we remove any additionally allocated memory before returning the line     the function to read lines of variable length  char  scan line char  line        int ch                 as getchar   returns  int      long capacity   0      capacity of the buffer     long length   0        maintains the length of the string     char  temp   NULL      use additional pointer to perform allocations in order to avoid memory leaks      while     ch   getchar         n    amp  amp   ch    EOF                  if  length   1   gt   capacity                           resetting capacity             if  capacity    0                  capacity   2     some initial fixed length              else                 capacity    2     double the size                 try reallocating the memory             if   temp   realloc line  capacity   sizeof char       NULL     allocating memory                               printf  quot ERROR  unsuccessful allocation quot                       return line  or you can exit                 exit 1                              line   temp                     line length     char  ch    type casting  int  to  char          length              line length   1      0     inserting null character at the end         remove additionally allocated memory     if   temp   realloc line   length   1    sizeof char       NULL                 printf  quot ERROR  unsuccessful allocation quot               return line  or you can exit         exit 1              line   temp      return line      Now you could read a full line this way    char  line   NULL   line   scan line line       Here s an example program using the scan line   function    include  lt stdio h gt   include  lt stdlib h gt    for dynamic allocation functions  char  scan line char  line                      int main void        char  a   NULL       a   scan line a     function call to scan the line      printf  quot  s n quot  a     printing the scanned line      free a     don t forget to free the malloc d pointer    sample input   Twinkle Twinkle little star     in the sky   sample output   Twinkle Twinkle little star     in the sky

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You need dynamic memory management  and use the fgets function to read your line  However  there seems to be no way to see how many characters it read  So you use fgetc   char   getline void        char   line   malloc 100     linep   line      size t lenmax   100  len   lenmax      int c       if line    NULL          return NULL       for               c   fgetc stdin           if c    EOF              break           if --len    0                len   lenmax              char   linen   realloc linep  lenmax    2                if linen    NULL                    free linep                   return NULL                            line   linen    line - linep               linep   linen                     if   line     c       n               break             line     0       return linep      Note  Never use gets   It does not do bounds checking and can overflow your buffer

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So  if you were looking for command arguments  take a look at Tim s answer  If you just want to read a line from console    include  lt stdio h gt   int main       char string  256     printf   Insert your full address        gets  string     printf   Your address is   s n  string     return 0      Yes  it is not secure  you can do buffer overrun  it does not check for end of file  it does not support encodings and a lot of other stuff  Actually I didn t even think whether it did ANY of this stuff   I agree I kinda screwed up    But   when I see a question like  How to read a line from the console in C    I assume a person needs something simple  like gets   and not 100 lines of code like above  Actually  I think  if you try to write those 100 lines of code in reality  you would do many more mistakes  than you would have done had you chosen gets

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If you are using the GNU C library or another POSIX-compliant library  you can use getline   and pass stdin to it for the file stream

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On BSD systems and Android you can also use fgetln    include  lt stdio h gt   char   fgetln FILE  stream  size t  len     Like so   size t line len  const char  line   fgetln stdin   amp line len     The line is not null terminated and contains  n  or whatever your platform is using  in the end  It becomes invalid after the next I O operation on stream

[c] How to read a line from the console in C?

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