ANSI escape sequences: colorize this DNA !

From Wikipedia: ANSI escape sequences are used to control text formatting, color, and other output options on text terminals. So you can try to type:

echo -e '\x1b[31mRED!\x1b[32mGREEN!\x1b[33mYELLOW!\x1b[0m'

in your favorite terminal, and you should get:

RED!GREEN!YELLOW!

It is then simple to create a simple 'C' program colorizing the content of a FASTA sequence.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include <unistd.h>
/*
from http://stackoverflow.com/questions/3219393/
http://en.wikipedia.org/wiki/ANSI_escape_code#Colors
*/
#define ANSI_COLOR_RED "\x1b[31m"
#define ANSI_COLOR_GREEN "\x1b[32m"
#define ANSI_COLOR_YELLOW "\x1b[33m"
#define ANSI_COLOR_BLUE "\x1b[34m"
#define ANSI_COLOR_MAGENTA "\x1b[35m"
#define ANSI_COLOR_CYAN "\x1b[36m"
#define ANSI_COLOR_BLACK "\x1b[0m"
#define ANSI_COLOR_RESET ANSI_COLOR_BLACK

static void fasta2term(FILE *in)
{
int prev_c=-1;
int c;

//not the terminal ? just 'cat'
if(!isatty(fileno(stdout)))
{
char buff[BUFSIZ];
int nRead;
while((nRead=fread(buff,1,BUFSIZ,in))>0)
{
fwrite(buff,1,nRead,stdout);
}
return;
}

while((c=fgetc(in))!=EOF)
{
if(c=='>')
{

if(prev_c!=-1) fputs(ANSI_COLOR_RESET,stdout);
fputc('>',stdout);
while((c=fgetc(in))!=EOF)
{
fputc(c,stdout);
if(c=='\n') break;
}
prev_c=-1;
continue;
}
else if(c==prev_c || isspace(c))
{
fputc(c,stdout);
continue;
}

switch(tolower(c))
{
case 'a': fputs(ANSI_COLOR_GREEN,stdout); break;
case 't': fputs(ANSI_COLOR_RED,stdout); break;
case 'g': fputs(ANSI_COLOR_BLACK,stdout); break;
case 'c': fputs(ANSI_COLOR_BLUE,stdout); break;
default: fputs(ANSI_COLOR_YELLOW,stdout); break;
}
fputc(c,stdout);
prev_c=c;
}
if(prev_c!=-1) fputs(ANSI_COLOR_RESET,stdout);
}

int main(int argc,char** argv)
{
int optind=1;
while(optind < argc)
{
if(strcmp(argv[optind],"-h")==0)
{
fprintf(stderr,"%s: Pierre Lindenbaum PHD. 2010.\n",argv[0]);
fprintf(stderr,"Compilation: %s at %s.\n",__DATE__,__TIME__);
exit(EXIT_FAILURE);
}
else if(strcmp(argv[optind],"--")==0)
{
++optind;
break;
}
else if(argv[optind][0]=='-')
{
fprintf(stderr,"unknown option '%s'\n",argv[optind]);
exit(EXIT_FAILURE);
}
else
{
break;
}
++optind;
}
if(optind==argc)
{
fasta2term(stdin);
}
else
{
while(optind< argc)
{
FILE* in;
errno=0;
in=fopen(argv[optind],"r");
if(in==NULL)
{
fprintf(stderr,"Cannot open %s : %s\n",argv[optind],strerror(errno));
return EXIT_FAILURE;
}
fasta2term(in);
fclose(in);
++optind;
}
}
return EXIT_SUCCESS;
}

Testing:

#compiling
gcc -o fasta2term -O3 -Wall fasta2term.c

#don't colorize when the output is piped into another program (=not a terminal)
./fasta2term ~/file.fasta | head -n 5
>gi|27592135
GGAAGGGCTGCCCCACCATTCATCCTTTTCTCGTAGTTTGTGCACGGTGCGGGAGGTTGTCTGAGTGACT
TCACGGGTCGCCTTTGTGCAGTACTAGATATGCAGCAGACCTATGACATGTGGCTAAAGAAACACAATCC
TGGGAAGCCTGGAGAGGGAACACCACTCACTTCGCGAGAAGGGGAGAAACAGATCCAGATGCCCACTGAC
TATGCTGACATCATGATGGGCTACCACTGCTGGCTCTGCGGGAAGAACAGCAACAGCAAGAAGCAATGGC

#do colorize if the output is a terminal
head -n5 ~/file.fasta | ./fasta2term
>gi|27592135
GGAAGGGCTGCCCCACCATTCATCCTTTTCTCGTAGTTTGTGCACGGTGCGGGAGGTTGTCTGAGTGACT
TCACGGGTCGCCTTTGTGCAGTACTAGATATGCAGCAGACCTATGACATGTGGCTAAAGAAACACAATCC
TGGGAAGCCTGGAGAGGGAACACCACTCACTTCGCGAGAAGGGGAGAAACAGATCCAGATGCCCACTGAC
TATGCTGACATCATGATGGGCTACCACTGCTGGCTCTGCGGGAAGAACAGCAACAGCAAGAAGCAATGGC

That's it

Pierre