How to extract numbers from string in c

Question

Say I have a string like ab234cid  s349  20kd and I want to extract all the numbers 234  349  20  what should I do

User · Accepted Answer

You can do it with strtol  like this   char  str    ab234cid  s349  20kd    p   str  while   p       While there are more characters to process        if   isdigit  p         p   -    p        amp  amp  isdigit   p 1                   Found a number         long val   strtol p   amp p  10      Read number         printf   ld n   val      and print it        else              Otherwise  move on to the next character          p              Link to ideone

User · Answer

A possible solution using sscanf   and scan sets   const char  s    ab234cid  s349  20kd   int i1  i2  i3  if  3    sscanf s                       0123456789  d    0123456789  d    0123456789  d                    amp i1                   amp i2                   amp i3         printf   d  d  d n   i1  i2  i3       where     0123456789  means ignore input until a digit is found  See demo at http   ideone com 2hB4UW    Or  if the number of numbers is unknown you can use  n specifier to record the last position read in the buffer   const char  s    ab234cid  s349  20kd   int total n   0  int n  int i  while  1    sscanf s   total n       0123456789  d n    amp i   amp n         total n    n      printf   d n   i

User · Answer

include lt stdio h gt   include lt ctype h gt   include lt stdlib h gt  void main int argc char  argv      char  str   ab234cid  s349  20kd    ptr   str  while   ptr       While there are more characters to process        if   isdigit  ptr                 Found a number         int val    int strtol ptr  amp ptr  10      Read number         printf   d n   val      and print it        else              Otherwise  move on to the next character          ptr

User · Answer

here after a simple solution using sscanf    include lt stdio h gt   include lt stdlib h gt   include lt string h gt   char str 256   ab234cid  s349  20kd   char tmp 256    int main          int x      tmp 0    0       while  sscanf str     0123456789  s  tmp str  gt 1  sscanf str   d s   amp x str                 if  tmp 0     0                         printf   d r n  x                     tmp 0    0

User · Answer

Or you can make a simple function like this      Provided  c  is only a numeric character int parseInt  char c        return c -  0

User · Answer

Make a state machine that operates on one basic principle  is the current character a number      When transitioning from non-digit to digit  you initialize your current number    number    when transitioning from digit to digit  you  shift  the new digit in  current number    current number   10   number  when transitioning from digit to non-digit  you output the current number when from non-digit to non-digit  you do nothing    Optimizations are possible

User · Answer

If the numbers are seprated by whitespace in the string then you can use sscanf    Since  it s not the case with your example   you have to do it yourself   char tmp 256    for i 0 str i  i        j 0    while str i  gt   0   amp  amp  str i  lt   9            tmp j  str i        i         j          tmp j  0    printf   ld   strtol tmp   amp tmp  10         Or store in an integer array

[c] How to extract numbers from string in c?

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