大型网站技术架构演进与性能优化,四川省建十五公司官网,wordpress清新模板,医疗网站模板免费下载linux的cat命令使用-n显示多个文件行号时#xff0c;行号是累加的#xff0c;不是到了新文件就重新计数。这样满足不了我的需求。如果到了新文件能够重新计数#xff0c;就能使用-nf#xff08;在上一篇-f显示文件名功能的基础上#xff09;加| grep xxx#xff0c;既能直…linux的cat命令使用-n显示多个文件行号时行号是累加的不是到了新文件就重新计数。这样满足不了我的需求。如果到了新文件能够重新计数就能使用-nf在上一篇-f显示文件名功能的基础上加| grep xxx既能直接显示xxx所在文件名又能直接显示xxx所在文件的行号。
对比效果
cat1是上一次编译的增加了-f功能但是没有重置行号的可执行文件。
bibosunny:~/work/coreutils/coreutils$ ../../cat/cat1 ./src/*.c -nf | grep full_write
./src/cat.c: 1777 if (full_write (STDOUT_FILENO, buf, n_read) ! n_read)
./src/cat.c: 1792 if (full_write (STDOUT_FILENO, outbuf, n_write) ! n_write)
./src/cat.c: 1856 if (full_write (STDOUT_FILENO, wp, outsize) ! outsize)
./src/cat.c: 2408 if (full_write (STDOUT_FILENO, \r, 1) ! 1)
./src/copy.c: 6643 if (full_write (dest_fd, pbuf, psize) ! psize)
./src/copy.c: 6739 if ((full_write (fd, zeros, n)) ! n)
./src/factor.c: 27708 if (full_write (STDOUT_FILENO, lbuf.buf, size) ! size)
./src/split.c: 66931 if (full_write (output_desc, bp, bytes) bytes)
./src/split.c: 67258 if (full_write (STDOUT_FILENO, bp, to_write) ! to_write)
./src/split.c: 67348 if (full_write (STDOUT_FILENO, buf, n_read) ! n_read
./src/split.c: 67515 if (full_write (STDOUT_FILENO, bp, to_write) ! to_write)
./src/split.c: 67533 if (full_write (files[i_file].ofd, bp, to_write) ! to_write
./src/yes.c: 85966 while (full_write (STDOUT_FILENO, buf, bufused) bufused)
bibosunny:~/work/coreutils/coreutils$ ./src/cat ./src/*.c -nf | grep full_write
./src/cat.c: 195 if (full_write (STDOUT_FILENO, buf, n_read) ! n_read)
./src/cat.c: 210 if (full_write (STDOUT_FILENO, outbuf, n_write) ! n_write)
./src/cat.c: 274 if (full_write (STDOUT_FILENO, wp, outsize) ! outsize)
./src/cat.c: 826 if (full_write (STDOUT_FILENO, \r, 1) ! 1)
./src/copy.c: 427 if (full_write (dest_fd, pbuf, psize) ! psize)
./src/copy.c: 523 if ((full_write (fd, zeros, n)) ! n)
./src/factor.c: 2365 if (full_write (STDOUT_FILENO, lbuf.buf, size) ! size)
./src/split.c: 632 if (full_write (output_desc, bp, bytes) bytes)
./src/split.c: 959 if (full_write (STDOUT_FILENO, bp, to_write) ! to_write)
./src/split.c: 1049 if (full_write (STDOUT_FILENO, buf, n_read) ! n_read
./src/split.c: 1216 if (full_write (STDOUT_FILENO, bp, to_write) ! to_write)
./src/split.c: 1234 if (full_write (files[i_file].ofd, bp, to_write) ! to_write
./src/yes.c: 125 while (full_write (STDOUT_FILENO, buf, bufused) bufused)
做出改动的源文件
./src/cat.c
使用sed将源文件中的windows的回车符\r去掉如果有回车符\r会提交失败这是在windows和linux来回传输文件并编辑文件导致的。
sed -i s/\r// ./src/cat.c
使用git add将./src/cat.c添加到暂存区
git add ./src/cat.c
使用git commit提交这次代码更新,-m表示备注信息备注信息必须要遵守原项目规定的格式否则会提交失败。
git commit -m cat: reset row number when open a new file
使用git log查看提交日志可以看到之前别人的提交备注信息都是简短的关键词加冒号再加简单的说明。
bibosunny:~/work/coreutils/coreutils$ git log
commit 64efc26d39266b72af029e8acf537f1f28a92c0a (HEAD - master)
Author: BIBO 120705103qq.com
Date: Fri Dec 29 11:22:31 2023 0800cat: reset row number when open a new filecommit 98d463ef5d44b9dfe6757942251164b56795b06f (origin/master, origin/HEAD)
Author: Christian Göttsche cgzonesgooglemail.com
Date: Tue Dec 19 15:55:28 2023 0100copy,install: avoid unnecessary security context translationsDo not perform SELinux context translation for operations not involvinguser input or output. Context translation converts MCS/MLS labels intohuman readable form, which is useful for user facing applications likels(1) or the --contextCTX argument of cp(1).* src/copy.c (set_process_security_ctx): Use raw selinux variants.* src/install.c (need_copy): Likewise.(setdefaultfilecon): Likewise.* src/selinux.c (computecon): Likewise.(defaultcon): Likewise.* tests/cp/no-ctx.sh: Add raw variants to preload lib.* NEWS: Mention the improvement.commit 343b8d7ba705c4e2a537bdc06ac6aa043e5f9e31
Author: Pádraig Brady PdraigBrady.com
Date: Tue Dec 19 17:18:46 2023 0000build: update gnulib to latest* gnulib: Primarily to get raw selinux wrappers
使用git diff加提交id查看提交前后的差异新的提交id放在后面看起来会更舒服显示的差异是增量。
bibosunny:~/work/coreutils/coreutils$ git diff 98d463ef5d44b9dfe6757942251164b56795b06f 64efc26d39266b72af029e8acf537f1f28a92c0a
diff --git a/src/cat.c b/src/cat.c
index e019faa8a..178c61c02 100644
--- a/src/cat.cb/src/cat.c-110,6 110,7 Concatenate FILE(s) to standard output.\n\-t equivalent to -vT\n\-T, --show-tabs display TAB characters as ^I\n\-u (ignored)\n\-f, --show-filename display filename at begin of each line\n\-v, --show-nonprinting use ^ and M- notation, except for LFD and TAB\n\), stdout);fputs (HELP_OPTION_DESCRIPTION, stdout);-126,6 127,22 Examples:\n\exit (status);}/* Reset line number */
static void
reset_line_num (void)
{line_num_print line_buf LINE_COUNTER_BUF_LEN - 8;line_num_start line_buf LINE_COUNTER_BUF_LEN - 3;line_num_end line_buf LINE_COUNTER_BUF_LEN - 3;for (int i 0; i 17; i){line_buf[i] ;}line_buf[17] 0;line_buf[18] \t;line_buf[19] \0;
}
/* Compute the next line number. */static void-211,7 228,7 write_pending (char *outbuf, char **bpout)static boolcat (char *inbuf, idx_t insize, char *outbuf, idx_t outsize,bool show_nonprinting, bool show_tabs, bool number, bool number_nonblank,
- bool show_ends, bool squeeze_blank)bool show_ends, bool squeeze_blank, bool show_filename){/* Last character read from the input buffer. */unsigned char ch;-395,6 412,13 cat (char *inbuf, idx_t insize, char *outbuf, idx_t outsize,pending_cr false;} /* Are we at the beginning of a line, and filename are requested? */if (newlines 0 show_filename){bpout stpcpy (bpout, infile);*bpout :;}
/* Are we at the beginning of a line, and line numbers are requested? */if (newlines 0 number)-547,6 571,7 main (int argc, char **argv)bool show_ends false;bool show_nonprinting false;bool show_tabs false;bool show_filename false;int file_open_mode O_RDONLY;static struct option const long_options[] -558,6 583,7 main (int argc, char **argv){show-ends, no_argument, nullptr, E},{show-tabs, no_argument, nullptr, T},{show-all, no_argument, nullptr, A},{show-filename, no_argument, nullptr, f},{GETOPT_HELP_OPTION_DECL},{GETOPT_VERSION_OPTION_DECL},{nullptr, 0, nullptr, 0}-578,7 604,7 main (int argc, char **argv)/* Parse command line options. */int c;
- while ((c getopt_long (argc, argv, benstuvAET, long_options, nullptr))while ((c getopt_long (argc, argv, befnstuvAET, long_options, nullptr))! -1){switch (c)-628,6 654,10 main (int argc, char **argv)show_tabs true;break; case f:show_filename true;break;
case_GETOPT_HELP_CHAR;case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);-667,6 697,8 main (int argc, char **argv)do{reset_line_num();
if (argind argc)infile argv[argind]; -722,7 754,7 main (int argc, char **argv)works, simple_cat otherwise. */if (! (number || show_ends || show_nonprinting
- || show_tabs || squeeze_blank))|| show_tabs || squeeze_blank || show_filename)){int copy_cat_status out_isreg S_ISREG (stat_buf.st_mode) ? copy_cat () : 0;-773,7 805,7 main (int argc, char **argv)ok cat (inbuf, insize, outbuf, outsize, show_nonprinting,show_tabs, number, number_nonblank, show_ends,
- squeeze_blank);squeeze_blank, show_filename);alignfree (outbuf);}修改后的./src/cat.c文件
/* cat -- concatenate files and print on the standard output.Copyright (C) 1988-2023 Free Software Foundation, Inc.This program is free software: you can redistribute it and/or modifyit under the terms of the GNU General Public License as published bythe Free Software Foundation, either version 3 of the License, or(at your option) any later version.This program is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See theGNU General Public License for more details.You should have received a copy of the GNU General Public Licensealong with this program. If not, see https://www.gnu.org/licenses/. *//* Differences from the Unix cat:* Always unbuffered, -u is ignored.* Usually much faster than other versions of cat, the differenceis especially apparent when using the -v option.By tegesics.se, Torbjörn Granlund, advised by rms, Richard Stallman. */#include config.h#include stdio.h
#include getopt.h
#include sys/types.h#if HAVE_STROPTS_H
# include stropts.h
#endif
#include sys/ioctl.h#include system.h
#include alignalloc.h
#include ioblksize.h
#include fadvise.h
#include full-write.h
#include safe-read.h
#include xbinary-io.h/* The official name of this program (e.g., no g prefix). */
#define PROGRAM_NAME cat#define AUTHORS \proper_name_lite (Torbjorn Granlund, Torbj\303\266rn Granlund), \proper_name (Richard M. Stallman)/* Name of input file. May be -. */
static char const *infile;/* Descriptor on which input file is open. */
static int input_desc;/* Buffer for line numbers.An 11 digit counter may overflow within an hour on a P2/466,an 18 digit counter needs about 1000y */
#define LINE_COUNTER_BUF_LEN 20
static char line_buf[LINE_COUNTER_BUF_LEN] { , , , , , , , , , , , , , , , , , 0,\t, \0};/* Position in line_buf where printing starts. This will not changeunless the number of lines is larger than 999999. */
static char *line_num_print line_buf LINE_COUNTER_BUF_LEN - 8;/* Position of the first digit in line_buf. */
static char *line_num_start line_buf LINE_COUNTER_BUF_LEN - 3;/* Position of the last digit in line_buf. */
static char *line_num_end line_buf LINE_COUNTER_BUF_LEN - 3;/* Preserves the cat functions local newlines between invocations. */
static int newlines2 0;/* Whether there is a pending CR to process. */
static bool pending_cr false;void
usage (int status)
{if (status ! EXIT_SUCCESS)emit_try_help ();else{printf (_(\
Usage: %s [OPTION]... [FILE]...\n\
),program_name);fputs (_(\
Concatenate FILE(s) to standard output.\n\
), stdout);emit_stdin_note ();fputs (_(\
\n\-A, --show-all equivalent to -vET\n\-b, --number-nonblank number nonempty output lines, overrides -n\n\-e equivalent to -vE\n\-E, --show-ends display $ at end of each line\n\-n, --number number all output lines\n\-s, --squeeze-blank suppress repeated empty output lines\n\
), stdout);fputs (_(\-t equivalent to -vT\n\-T, --show-tabs display TAB characters as ^I\n\-u (ignored)\n\-f, --show-filename display filename at begin of each line\n\-v, --show-nonprinting use ^ and M- notation, except for LFD and TAB\n\
), stdout);fputs (HELP_OPTION_DESCRIPTION, stdout);fputs (VERSION_OPTION_DESCRIPTION, stdout);printf (_(\
\n\
Examples:\n\%s f - g Output fs contents, then standard input, then gs contents.\n\%s Copy standard input to standard output.\n\
),program_name, program_name);emit_ancillary_info (PROGRAM_NAME);}exit (status);
}/* Reset line number */
static void
reset_line_num (void)
{line_num_print line_buf LINE_COUNTER_BUF_LEN - 8;line_num_start line_buf LINE_COUNTER_BUF_LEN - 3;line_num_end line_buf LINE_COUNTER_BUF_LEN - 3;for (int i 0; i 17; i){line_buf[i] ;}line_buf[17] 0;line_buf[18] \t;line_buf[19] \0;
}/* Compute the next line number. */static void
next_line_num (void)
{char *endp line_num_end;do{if ((*endp) 9)return;*endp-- 0;}while (endp line_num_start);if (line_num_start line_buf)*--line_num_start 1;else*line_buf ;if (line_num_start line_num_print)line_num_print--;
}/* Plain cat. Copy the file behind input_desc to STDOUT_FILENO.BUF (of size BUFSIZE) is the I/O buffer, used by reads and writes.Return true if successful. */static bool
simple_cat (char *buf, idx_t bufsize)
{/* Loop until the end of the file. */while (true){/* Read a block of input. */size_t n_read safe_read (input_desc, buf, bufsize);if (n_read SAFE_READ_ERROR){error (0, errno, %s, quotef (infile));return false;}/* End of this file? */if (n_read 0)return true;/* Write this block out. */if (full_write (STDOUT_FILENO, buf, n_read) ! n_read)write_error ();}
}/* Write any pending output to STDOUT_FILENO.Pending is defined to be the *BPOUT - OUTBUF bytes starting at OUTBUF.Then set *BPOUT to OUTPUT if its not already that value. */static inline void
write_pending (char *outbuf, char **bpout)
{idx_t n_write *bpout - outbuf;if (0 n_write){if (full_write (STDOUT_FILENO, outbuf, n_write) ! n_write)write_error ();*bpout outbuf;}
}/* Copy the file behind input_desc to STDOUT_FILENO.Use INBUF and read INSIZE with each call,and OUTBUF and write OUTSIZE with each call.(The buffers are a bit larger than the I/O sizes.)The remaining boolean args say what cat options to use.Return true if successful.Called if any option more than -u was specified.A newline character is always put at the end of the buffer, to makean explicit test for buffer end unnecessary. */static bool
cat (char *inbuf, idx_t insize, char *outbuf, idx_t outsize,bool show_nonprinting, bool show_tabs, bool number, bool number_nonblank,bool show_ends, bool squeeze_blank, bool show_filename)
{/* Last character read from the input buffer. */unsigned char ch;/* Determines how many consecutive newlines there have been in theinput. 0 newlines makes NEWLINES -1, 1 newline makes NEWLINES 1,etc. Initially 0 to indicate that we are at the beginning of anew line. The state of the procedure is determined byNEWLINES. */int newlines newlines2;#ifdef FIONREAD/* If nonzero, use the FIONREAD ioctl, as an optimization.(On Ultrix, it is not supported on NFS file systems.) */bool use_fionread true;
#endif/* The inbuf pointers are initialized so that BPIN EOB, and thereby inputis read immediately. *//* Pointer to the first non-valid byte in the input buffer, i.e., thecurrent end of the buffer. */char *eob inbuf;/* Pointer to the next character in the input buffer. */char *bpin eob 1;/* Pointer to the position where the next character shall be written. */char *bpout outbuf;while (true){do{/* Write if there are at least OUTSIZE bytes in OUTBUF. */if (outbuf outsize bpout){char *wp outbuf;idx_t remaining_bytes;do{if (full_write (STDOUT_FILENO, wp, outsize) ! outsize)write_error ();wp outsize;remaining_bytes bpout - wp;}while (outsize remaining_bytes);/* Move the remaining bytes to the beginning of thebuffer. */memmove (outbuf, wp, remaining_bytes);bpout outbuf remaining_bytes;}/* Is INBUF empty? */if (bpin eob){bool input_pending false;
#ifdef FIONREADint n_to_read 0;/* Is there any input to read immediately?If not, we are about to wait,so write all buffered output before waiting. */if (use_fionread ioctl (input_desc, FIONREAD, n_to_read) 0){/* Ultrix returns EOPNOTSUPP on NFS;HP-UX returns ENOTTY on pipes.SunOS returns EINVAL andMore/BSD returns ENODEV on special fileslike /dev/null.Irix-5 returns ENOSYS on pipes. */if (errno EOPNOTSUPP || errno ENOTTY|| errno EINVAL || errno ENODEV|| errno ENOSYS)use_fionread false;else{error (0, errno, _(cannot do ioctl on %s),quoteaf (infile));newlines2 newlines;return false;}}if (n_to_read ! 0)input_pending true;
#endifif (!input_pending)write_pending (outbuf, bpout);/* Read more input into INBUF. */size_t n_read safe_read (input_desc, inbuf, insize);if (n_read SAFE_READ_ERROR){error (0, errno, %s, quotef (infile));write_pending (outbuf, bpout);newlines2 newlines;return false;}if (n_read 0){write_pending (outbuf, bpout);newlines2 newlines;return true;}/* Update the pointers and insert a sentinel at the bufferend. */bpin inbuf;eob bpin n_read;*eob \n;}else{/* It was a real (not a sentinel) newline. *//* Was the last line empty?(i.e., have two or more consecutive newlines been read?) */if (newlines 0){if (newlines 2){/* Limit this to 2 here. Otherwise, with lots ofconsecutive newlines, the counter could wraparound at INT_MAX. */newlines 2;/* Are multiple adjacent empty lines to be substitutedby single ditto (-s), and this was the second emptyline? */if (squeeze_blank){ch *bpin;continue;}}/* Are line numbers to be written at empty lines (-n)? */if (number !number_nonblank){next_line_num ();bpout stpcpy (bpout, line_num_print);}}/* Output a currency symbol if requested (-e). */if (show_ends){if (pending_cr){*bpout ^;*bpout M;pending_cr false;}*bpout $;}/* Output the newline. */*bpout \n;}ch *bpin;}while (ch \n);/* Here CH cannot contain a newline character. */if (pending_cr){*bpout \r;pending_cr false;}/* Are we at the beginning of a line, and filename are requested? */if (newlines 0 show_filename){bpout stpcpy (bpout, infile);*bpout :;}/* Are we at the beginning of a line, and line numbers are requested? */if (newlines 0 number){next_line_num ();bpout stpcpy (bpout, line_num_print);}/* The loops below continue until a newline character is found,which means that the buffer is empty or that a proper newlinehas been found. *//* If quoting, i.e., at least one of -v, -e, or -t specified,scan for chars that need conversion. */if (show_nonprinting){while (true){if (ch 32){if (ch 127)*bpout ch;else if (ch 127){*bpout ^;*bpout ?;}else{*bpout M;*bpout -;if (ch 128 32){if (ch 128 127)*bpout ch - 128;else{*bpout ^;*bpout ?;}}else{*bpout ^;*bpout ch - 128 64;}}}else if (ch \t !show_tabs)*bpout \t;else if (ch \n){newlines -1;break;}else{*bpout ^;*bpout ch 64;}ch *bpin;}}else{/* Not quoting, neither of -v, -e, or -t specified. */while (true){if (ch \t show_tabs){*bpout ^;*bpout ch 64;}else if (ch ! \n){if (ch \r *bpin \n show_ends){if (bpin eob)pending_cr true;else{*bpout ^;*bpout M;}}else*bpout ch;}else{newlines -1;break;}ch *bpin;}}}
}/* Copy data from input to output using copy_file_range if possible.Return 1 if successful, 0 if ordinary readwrite should be tried,-1 if a serious problem has been diagnosed. */static int
copy_cat (void)
{/* Copy at most COPY_MAX bytes at a time; this is min(SSIZE_MAX, SIZE_MAX) truncated to a value that issurely aligned well. */ssize_t copy_max MIN (SSIZE_MAX, SIZE_MAX) 30 30;/* copy_file_range does not support some cases, and itincorrectly returns 0 when reading from the proc filesystem on the Linux kernel through at least 5.6.19 (2020),so fall back on readwrite if the copy_file_range isunsupported or the input file seems empty. */for (bool some_copied false; ; some_copied true)switch (copy_file_range (input_desc, nullptr, STDOUT_FILENO, nullptr,copy_max, 0)){case 0:return some_copied;case -1:if (errno ENOSYS || is_ENOTSUP (errno) || errno EINVAL|| errno EBADF || errno EXDEV || errno ETXTBSY|| errno EPERM)return 0;error (0, errno, %s, quotef (infile));return -1;}
}int
main (int argc, char **argv)
{/* Nonzero if we have ever read standard input. */bool have_read_stdin false;struct stat stat_buf;/* Variables that are set according to the specified options. */bool number false;bool number_nonblank false;bool squeeze_blank false;bool show_ends false;bool show_nonprinting false;bool show_tabs false;bool show_filename false;int file_open_mode O_RDONLY;static struct option const long_options[] {{number-nonblank, no_argument, nullptr, b},{number, no_argument, nullptr, n},{squeeze-blank, no_argument, nullptr, s},{show-nonprinting, no_argument, nullptr, v},{show-ends, no_argument, nullptr, E},{show-tabs, no_argument, nullptr, T},{show-all, no_argument, nullptr, A},{show-filename, no_argument, nullptr, f},{GETOPT_HELP_OPTION_DECL},{GETOPT_VERSION_OPTION_DECL},{nullptr, 0, nullptr, 0}};initialize_main (argc, argv);set_program_name (argv[0]);setlocale (LC_ALL, );bindtextdomain (PACKAGE, LOCALEDIR);textdomain (PACKAGE);/* Arrange to close stdout if we exit via thecase_GETOPT_HELP_CHAR or case_GETOPT_VERSION_CHAR code.Normally STDOUT_FILENO is used rather than stdout, soclose_stdout does nothing. */atexit (close_stdout);/* Parse command line options. */int c;while ((c getopt_long (argc, argv, befnstuvAET, long_options, nullptr))! -1){switch (c){case b:number true;number_nonblank true;break;case e:show_ends true;show_nonprinting true;break;case n:number true;break;case s:squeeze_blank true;break;case t:show_tabs true;show_nonprinting true;break;case u:/* We provide the -u feature unconditionally. */break;case v:show_nonprinting true;break;case A:show_nonprinting true;show_ends true;show_tabs true;break;case E:show_ends true;break;case T:show_tabs true;break;case f:show_filename true;break;case_GETOPT_HELP_CHAR;case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);default:usage (EXIT_FAILURE);}}/* Get device, i-node number, and optimal blocksize of output. */if (fstat (STDOUT_FILENO, stat_buf) 0)error (EXIT_FAILURE, errno, _(standard output));/* Optimal size of i/o operations of output. */idx_t outsize io_blksize (stat_buf);/* Device and I-node number of the output. */dev_t out_dev stat_buf.st_dev;ino_t out_ino stat_buf.st_ino;/* True if the output is a regular file. */bool out_isreg S_ISREG (stat_buf.st_mode) ! 0;if (! (number || show_ends || squeeze_blank)){file_open_mode | O_BINARY;xset_binary_mode (STDOUT_FILENO, O_BINARY);}/* Main loop. */infile -;int argind optind;bool ok true;idx_t page_size getpagesize ();do{reset_line_num();if (argind argc)infile argv[argind];bool reading_stdin STREQ (infile, -);if (reading_stdin){have_read_stdin true;input_desc STDIN_FILENO;if (file_open_mode O_BINARY)xset_binary_mode (STDIN_FILENO, O_BINARY);}else{input_desc open (infile, file_open_mode);if (input_desc 0){error (0, errno, %s, quotef (infile));ok false;continue;}}if (fstat (input_desc, stat_buf) 0){error (0, errno, %s, quotef (infile));ok false;goto contin;}/* Optimal size of i/o operations of input. */idx_t insize io_blksize (stat_buf);fdadvise (input_desc, 0, 0, FADVISE_SEQUENTIAL);/* Dont copy a nonempty regular file to itself, as that wouldmerely exhaust the output device. Its better to catch thiserror earlier rather than later. */if (out_isreg stat_buf.st_dev out_dev stat_buf.st_ino out_ino lseek (input_desc, 0, SEEK_CUR) stat_buf.st_size){error (0, 0, _(%s: input file is output file), quotef (infile));ok false;goto contin;}/* Pointer to the input buffer. */char *inbuf;/* Select which version of cat to use. If any format-orientedoptions were given use cat; if not, use copy_cat if itworks, simple_cat otherwise. */if (! (number || show_ends || show_nonprinting|| show_tabs || squeeze_blank || show_filename)){int copy_cat_status out_isreg S_ISREG (stat_buf.st_mode) ? copy_cat () : 0;if (copy_cat_status ! 0){inbuf nullptr;ok 0 copy_cat_status;}else{insize MAX (insize, outsize);inbuf xalignalloc (page_size, insize);ok simple_cat (inbuf, insize);}}else{/* Allocate, with an extra byte for a newline sentinel. */inbuf xalignalloc (page_size, insize 1);/* Why are(OUTSIZE - 1 INSIZE * 4 LINE_COUNTER_BUF_LEN)bytes allocated for the output buffer?A test whether output needs to be written is done when the inputbuffer empties or when a newline appears in the input. Afteroutput is written, at most (OUTSIZE - 1) bytes will remain in thebuffer. Now INSIZE bytes of input is read. Each input charactermay grow by a factor of 4 (by the prepending of M-^). If allcharacters do, and no newlines appear in this block of input, wewill have at most (OUTSIZE - 1 INSIZE * 4) bytes in the buffer.If the last character in the preceding block of input was anewline, a line number may be written (according to the givenoptions) as the first thing in the output buffer. (Done after thenew input is read, but before processing of the input begins.)A line number requires seldom more than LINE_COUNTER_BUF_LENpositions.Align the output buffer to a page size boundary, for efficiencyon some paging implementations. */idx_t bufsize;if (ckd_mul (bufsize, insize, 4)|| ckd_add (bufsize, bufsize, outsize)|| ckd_add (bufsize, bufsize, LINE_COUNTER_BUF_LEN - 1))xalloc_die ();char *outbuf xalignalloc (page_size, bufsize);ok cat (inbuf, insize, outbuf, outsize, show_nonprinting,show_tabs, number, number_nonblank, show_ends,squeeze_blank, show_filename);alignfree (outbuf);}alignfree (inbuf);contin:if (!reading_stdin close (input_desc) 0){error (0, errno, %s, quotef (infile));ok false;}}while (argind argc);if (pending_cr){if (full_write (STDOUT_FILENO, \r, 1) ! 1)write_error ();}if (have_read_stdin close (STDIN_FILENO) 0)error (EXIT_FAILURE, errno, _(closing standard input));return ok ? EXIT_SUCCESS : EXIT_FAILURE;
}
