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author | Rob Landley <rob@landley.net> | 2012-08-25 14:25:22 -0500 |
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committer | Rob Landley <rob@landley.net> | 2012-08-25 14:25:22 -0500 |
commit | 3a9241add947cb6d24b5de7a8927517426a78795 (patch) | |
tree | d122ab6570439cd6b17c7d73ed8d4e085e0b8a95 /toys/tail.c | |
parent | 689f095bc976417bf50810fe59a3b3ac32b21105 (diff) | |
download | toybox-3a9241add947cb6d24b5de7a8927517426a78795.tar.gz |
Move commands into "posix", "lsb", and "other" menus/directories.
Diffstat (limited to 'toys/tail.c')
-rw-r--r-- | toys/tail.c | 232 |
1 files changed, 0 insertions, 232 deletions
diff --git a/toys/tail.c b/toys/tail.c deleted file mode 100644 index 8783d6ba..00000000 --- a/toys/tail.c +++ /dev/null @@ -1,232 +0,0 @@ -/* vi: set sw=4 ts=4: - * - * tail.c - copy last lines from input to stdout. - * - * Copyright 2012 Timothy Elliott <tle@holymonkey.com> - * - * See http://www.opengroup.org/onlinepubs/009695399/utilities/tail.html - -USE_TAIL(NEWTOY(tail, "fc-n-", TOYFLAG_BIN)) - -config TAIL - bool "tail" - default y - help - usage: tail [-n|c number] [-f] [file...] - - Copy last lines from files to stdout. If no files listed, copy from - stdin. Filename "-" is a synonym for stdin. - - -n output the last X lines (default 10), +X counts from start. - -c output the last X bytes, +X counts from start - -f follow file, waiting for more data to be appended - -config TAIL_SEEK - bool "tail seek support" - default y - depends on TAIL - help - This version uses lseek, which is faster on large files. -*/ - -#include "toys.h" - -DEFINE_GLOBALS( - long lines; - long bytes; - - int file_no; -) - -#define TT this.tail - -#define FLAG_n 1 -#define FLAG_c 2 -#define FLAG_f 4 - -struct line_list { - struct line_list *next, *prev; - char *data; - int len; -}; - -static struct line_list *get_chunk(int fd, int len) -{ - struct line_list *line = xmalloc(sizeof(struct line_list)+len); - - line->data = ((char *)line) + sizeof(struct line_list); - line->len = readall(fd, line->data, len); - - if (line->len < 1) { - free(line); - return 0; - } - - return line; -} - -static void dump_chunk(void *ptr) -{ - struct line_list *list = ptr; - xwrite(1, list->data, list->len); - free(list); -} - -// Reading through very large files is slow. Using lseek can speed things -// up a lot, but isn't applicable to all input (cat | tail). -// Note: bytes and lines are negative here. -static int try_lseek(int fd, long bytes, long lines) -{ - struct line_list *list = 0, *temp; - int flag = 0, chunk = sizeof(toybuf); - ssize_t pos = lseek(fd, 0, SEEK_END); - - // If lseek() doesn't work on this stream, return now. - if (pos<0) return 0; - - // Seek to the right spot, output data from there. - if (bytes) { - if (lseek(fd, bytes, SEEK_END)<0) lseek(fd, 0, SEEK_SET); - xsendfile(fd, 1); - return 1; - } - - // Read from end to find enough lines, then output them. - - bytes = pos; - while (lines && pos) { - int offset; - - // Read in next chunk from end of file - if (chunk>pos) chunk = pos; - pos -= chunk; - if (pos != lseek(fd, pos, SEEK_SET)) { - perror_msg("seek failed"); - break; - } - if (!(temp = get_chunk(fd, chunk))) break; - if (list) list->next = temp; - list = temp; - - // Count newlines in this chunk. - offset = list->len; - while (offset--) { - // If the last line ends with a newline, that one doesn't count. - if (!flag) { - flag++; - - continue; - } - - // Start outputting data right after newline - if (list->data[offset] == '\n' && !++lines) { - offset++; - list->data += offset; - list->len -= offset; - - break; - } - } - } - - // Output stored data - llist_traverse(list, dump_chunk); - - // In case of -f - lseek(fd, bytes, SEEK_SET); - return 1; -} - -// Called for each file listed on command line, and/or stdin -static void do_tail(int fd, char *name) -{ - long bytes = TT.bytes, lines = TT.lines; - - if (toys.optc > 1) { - if (TT.file_no++) xputc('\n'); - xprintf("==> %s <==\n", name); - } - - // Are we measuring from the end of the file? - - if (bytes<0 || lines<0) { - struct line_list *list = 0, *new; - - // The slow codepath is always needed, and can handle all input, - // so make lseek support optional. - if (CFG_TAIL_SEEK && try_lseek(fd, bytes, lines)); - - // Read data until we run out, keep a trailing buffer - else for (;;) { - int len, count; - char *try; - - if (!(new = get_chunk(fd, sizeof(toybuf)))) break; - // append in order - dlist_add_nomalloc((struct double_list **)&list, - (struct double_list *)new); - - // Measure new chunk, discarding extra data from buffer - len = new->len; - try = new->data; - for (count=0; count<len; count++) { - if ((toys.optflags & FLAG_c) && bytes) { - bytes++; - continue; - } - - if (lines) { - if(try[count] != '\n' && count != len-1) continue; - if (lines<0) { - if (!++lines) ++lines; - continue; - } - } - - // Time to discard data; given that bytes and lines were - // nonzero coming in, we can't discard too much if we're - // measuring right. - do { - char c = *(list->data++); - if (!(--list->len)) { - struct line_list *next = list->next; - list->prev->next = next; - list->next->prev = list->prev; - free(list); - list = next; - } - if (c == '\n') break; - } while (lines); - } - } - - // Output/free the buffer. - llist_traverse(list, dump_chunk); - - // Measuring from the beginning of the file. - } else for (;;) { - int len, offset = 0; - - // Error while reading does not exit. Error writing does. - len = read(fd, toybuf, sizeof(toybuf)); - if (len<1) break; - while (bytes > 1 || lines > 1) { - bytes--; - if (toybuf[offset++] == '\n') lines--; - if (offset >= len) break; - } - if (offset<len) xwrite(1, toybuf+offset, len-offset); - } - - // -f support: cache name/descriptor -} - -void tail_main(void) -{ - // if nothing specified, default -n to -10 - if (!(toys.optflags&(FLAG_n|FLAG_c))) TT.lines = -10; - - loopfiles(toys.optargs, do_tail); - - // do -f stuff -} |