ref: 02a26802ffbd64ebf993119e1599920ffee01ef0
dir: /sys/src/cmd/read.c/
#include <u.h> #include <libc.h> int multi; int nlines; vlong nchars; char *status = nil; int line(int fd, char *file) { char c; int m, n, nalloc; char *buf; nalloc = 0; buf = nil; for(m=0; ; ){ n = read(fd, &c, 1); if(n < 0){ fprint(2, "read: error reading %s: %r\n", file); exits("read error"); } if(n == 0){ if(m == 0) status = "eof"; break; } if(m == nalloc){ nalloc += 1024; buf = realloc(buf, nalloc); if(buf == nil){ fprint(2, "read: malloc error: %r\n"); exits("malloc"); } } buf[m++] = c; if(c == '\n') break; } if(m > 0) write(1, buf, m); free(buf); return m; } void lines(int fd, char *file) { do{ if(line(fd, file) == 0) break; }while(multi || --nlines>0); } void chars(int fd, char *file) { char buf[8*1024]; vlong m; int n; for(m = 0; m < nchars; m += n){ n = sizeof(buf); if(n > (nchars - m)) n = nchars - m; if((n = read(fd, buf, n)) < 0){ fprint(2, "read: error reading %s: %r\n", file); exits("read error"); } if(n == 0){ if(m == 0) status = "eof"; break; } write(1, buf, n); } } void usage(void) { fprint(2, "usage: read [-m] [-n nlines] [-c nbytes] [files...]\n"); exits("usage"); } void main(int argc, char *argv[]) { void (*proc)(int, char*); int i, fd; proc = lines; ARGBEGIN{ case 'c': nchars = atoll(EARGF(usage())); proc = chars; break; case 'n': nlines = atoi(EARGF(usage())); break; case 'm': multi = 1; break; default: usage(); }ARGEND if(argc == 0) (*proc)(0, "<stdin>"); else for(i=0; i<argc; i++){ fd = open(argv[i], OREAD); if(fd < 0){ fprint(2, "read: can't open %s: %r\n", argv[i]); exits("open"); } (*proc)(fd, argv[i]); close(fd); } exits(status); }