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Make 1992/adrian use fgets() not gets()

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There was only one call to gets() and one call to fgets(). gets() reads
from stdin so the fgets() call has to as well. But why was it using
gets() and not fgets()? My guess is because fgets() stores the final
newline which means that the output had extra lines. The entry was
relying on this string NOT having a newline printed after the line
matched! Having a newline in turn broke the generation of some output
like that of adhead.c. Thus if fgets() != NULL we trim off the trailing
newline first. This allows the entry and all generated code to compile
successfully (adhead.c ended up having a multi-line macro messed up
because of an empty line after the \ at the end of the line). Since
gets() does not store the final newline and since we trim that off the
code is functionally equivalent but now safer.
This commit is contained in:
Cody Boone Ferguson committed 2023-03-28 04:17:43 -07:00
1 parent 4594e02036
commit 59c95a86d5
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+150 -123
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1992/adrian/README.md
+149 -121
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@@ -11,6 +11,20 @@
make all
[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) changed the location
that it used `gets()` to be `fgets()` instead to make it safer. One might think
that simply changing the gets() to fgets() (with stdin) would work but it did
not because `fgets()` stores the newline and `gets()` does not. The code was
relying on not having this newline. With `fgets()` the code `if(A(Y)) puts(Y);`
ended up printing an extra line which made the generation of some files (like
`adhead.c`) fail to compile (`gets()` does not store the newline but `fgets()`
does). Why? There was a blank line after a `\` at the end of the first line of a
macro definition! Thus the code now first trims off the last character of the
buffer read to get the same correct functionality but in a safe way. Thank you
Cody for your assistance!
## Try:
./adrian adrian.grep.try < README.md
@@ -19,56 +33,56 @@ For the slow minded, try:
./adsleep 32767
## Judges' comments
## Judges' comments:
Once you get past the obfuscation, you have an opportunity to learn
about regular expressions and state machines.
Once you get past the obfuscation, you have an opportunity to learn
about regular expressions and state machines.
NOTE: Some compilers have had trouble optimizing this entry.
NOTE: Some compilers have had trouble optimizing this entry.
## Author's comments
## Author's comments:
ADrian's GREP (adgrep)
ADrian's GREP (adgrep)
For those confused by the complexity of full-blown egrep style regular
expressions, this program offers an alternative. It implements an
equivalent search, using a deterministic finite automaton.
For those confused by the complexity of full-blown egrep style regular
expressions, this program offers an alternative. It implements an
equivalent search, using a deterministic finite automaton.
A deterministic finite automaton consists of a finite set of states,
along with transition rules to move from one state to another, an initial
state, and a set of accepting states. The automaton takes a string as
input and begins in the start state. It reads a character of the string
and consults the rules for the current state, moving to the new state
indicated by the appropriate rule. This process is repeated until the
string is consumed. If the current state at this point is one of the
accepting states, then the string is accepted.
A deterministic finite automaton consists of a finite set of states,
along with transition rules to move from one state to another, an initial
state, and a set of accepting states. The automaton takes a string as
input and begins in the start state. It reads a character of the string
and consults the rules for the current state, moving to the new state
indicated by the appropriate rule. This process is repeated until the
string is consumed. If the current state at this point is one of the
accepting states, then the string is accepted.
The deterministic finite automaton is specified as a series of rules for
each state:
The deterministic finite automaton is specified as a series of rules for
each state:
<state> chars1 <dest1> chars2 <dest2> ...
chars1 is a list of characters (only the first 8 are significant) which
should trigger a transition to <dest1>. <dest1> is another state which
should have a similar specification somewhere. A state is accepting if
it is specified in square brackets: [final], and state strings are
significant to only eight characters.
`chars1` is a list of characters (only the first 8 are significant) which
should trigger a transition to `<dest1>`. `<dest1>` is another state which
should have a similar specification somewhere. A state is accepting if
it is specified in square brackets: `[final]`, and state strings are
significant to only eight characters.
Example 1: matches ^abc$
### Example 1: matches `^abc$`
<q0> a <q1> The first state to appear is the start state
<q1> b <q2>
<q2> c [q3]
[q3]
Technically, a deterministic finite automaton should have a rule for each
possible input character at each state. To simplify descriptions of the
automata, if no rule is present, the string will not be accepted. Also,
the '.' character matches any character if it occurs first in the
character list.
Technically, a deterministic finite automaton should have a rule for each
possible input character at each state. To simplify descriptions of the
automata, if no rule is present, the string will not be accepted. Also,
the `'.'` character matches any character if it occurs first in the
character list.
Example 2: ^abc
### Example 2: `^abc`
<q0> a <q1>
<q1> b <q2>
@@ -76,7 +90,7 @@ For the slow minded, try:
[q3] . [q3]
Example 3: abc$
### Example 3: `abc$`
<q0> a <q1> . <q0>
<q1> b <q2> a <q1> . <q0>
@@ -84,14 +98,14 @@ For the slow minded, try:
[q3] . <q1>
Example 4: ^(abc)*$
### Example 4: `^(abc)*$`
[q0] a <q1>
<q1> b <q2>
<q2> c [q0]
Example 5: ^[ab][cd][ef]$
### Example 5: `^[ab][cd][ef]$`
<q0> ab <q1>
<q1> cd <q2>
@@ -99,7 +113,7 @@ For the slow minded, try:
[q3]
Example 6: ^(abc|efg)$
### Example 6: `^(abc|efg)$`
<q0> a <q1> e <q3>
<q1> b <q2>
@@ -109,118 +123,132 @@ For the slow minded, try:
[q5]
With the automaton specification in 'filename', invoke the program by
typing
With the automaton specification in 'filename', invoke the program by
typing
adgrep 'filename'
It will read stdin and print out all the lines which the automaton
accepts. If the file cannot be opened, a system error message will
be printed. If the input contains errors, then an error message along
with the number of the offending line will be printed to stderr. The
number of rules for each state is limited to 17. If more than 17 rules
are present, you get the error to_many_rules, and the state that was
being processed is printed. Error no_destination occurs if you specify a
set of characters, but no destination state, and error too_many_states
occurs if your automaton has more than 257 states.
Running
adgrep from < your_mailbox
will perform a function similar to that of the unix from command.
If no filename is specified on the command line, then "adgrep.c" is used
as the specification for the automaton. (This file has been renamed
to adrian.c by the judges.) In this case, the program will search for
matches to the regular expression:
^.[^|C][^w[Q]*(Q|[w[]c).*|^.[C|]$
I suggest using adgrep.c as input, and storing the output in adwc.c:
adgrep < adgrep.c > adwc.c
Compiling the new file, mywc.c, yields a clone of the unix wc command. It
runs on one file (defaulting to "adgrep.c" if no file is given) and
displays the number of lines, words, and bytes in the input file.
```sh
./adgrep 'filename'
```
Another possibly interesting automaton can be created by slightly
adjusting the adgrep.c file. Change the first line to read
It will read stdin and print out all the lines which the automaton
accepts. If the file cannot be opened, a system error message will
be printed. If the input contains errors, then an error message along
with the number of the offending line will be printed to stderr. The
number of rules for each state is limited to 17. If more than 17 rules
are present, you get the error `too_many_rules`, and the state that was
being processed is printed. Error `no_destination` occurs if you specify a
set of characters, but no destination state, and error `too_many_states`
occurs if your automaton has more than 257 states.
/* . echo| . */
Running:
and repeat the process above
```sh
./adgrep from < your_mailbox
```
adgrep <adgrep.c > adecho.c
will perform a function similar to that of the unix from command.
The new file now contains all lines which match
^.[^5|m^]*[m^]([e=p,;]|[^e=+p,;].*)$
Compile and run. This is an echo clone. Note the efficient algorithm
employed.
If no filename is specified on the command line, then `"adgrep.c"` is used
as the specification for the automaton. (This file has been renamed
to `adrian.c` by the judges.) In this case, the program will search for
matches to the regular expression:
Two other adjustments to the first line also yield useful results. By
changing it to
/* . head; . */
^.[^|C][^w[Q]*(Q|[w[]c).*|^.[C|]$
you can search for matches to
I suggest using `adgrep.c` as input, and storing the output in `adwc.c`:
^.[^W]*W..*$
```sh
./adgrep < adgrep.c > adwc.c
```
By some freak happenstance, lines of adgrep.c which match this regular
expression form a unix head command. It prints the first ten lines of
the file specified on the command line (or adgrep.c if no file is
specified).
Compiling the new file, `mywc.c`, yields a clone of the unix wc command. It
runs on one file (defaulting to `"adgrep.c"` if no file is given) and
displays the number of lines, words, and bytes in the input file.
By setting the first line to
/* . basename . */
Another possibly interesting automaton can be created by slightly
adjusting the `adgrep.c` file. Change the first line to read
a clone of the unix basename command can be unearthed. The automaton will
search for
^.[^j]*jr.*$
/* . echo| . */
on standard input. And the program which results by running adgrep.c
through this filter requires two parameters. The first is meant to be a
filename, and the second, an extension. All leading pathname components
are removed from the filename, and the extension is removed if present.
The resulting base name is printed to stdout.
and repeat the process above
Lastly, by setting the first line to
```sh
./adgrep <adgrep.c > adecho.c
```
/* . sleep . */
The new file now contains all lines which match
you can search for
^.[^5|m^]*[m^]([e=p,;]|[^e=+p,;].*)$
^.[^(~][^s]*sl.*$
Compile and run. This is an echo clone. Note the efficient algorithm
employed.
Filtering adgrep.c through this search yields a clone of the sleep
command. Invoke with a single integer parameter, and it will pause
for that many seconds.
If either adbasename or adsleep is invoked with too few parameters,
the program will print the error message:
Segmentation fault (core dumped)
Two other adjustments to the first line also yield useful results. By
changing it to
(The exact text of the above error messages varies from machine to
machine.) The four programs which read from stdin require lines
shorter than 999 characters.
/* . head; . */
The other info files are adrian.grep.[1-6] which contain the six
examples that appear above, and from, which is used to emulate the
unix from command. For reasons of clarity, the name "from" should
probably not be changed if possible. I wouldn't want to be accused of
confusing people by giving the input files weird names.
you can search for matches to
If you want to change the default input filename (line 80) you must be
careful to choose a name that doesn't match the wrong search patterns,
introducing extra lines into one of the programs.
^.[^W]*W..*$
The program will produce at least one warning and possible several
when compiled depending on the compiler.
By some freak happenstance, lines of adgrep.c which match this regular
expression form a unix head command. It prints the first ten lines of
the file specified on the command line (or adgrep.c if no file is
specified).
By setting the first line to
/* . basename . */
a clone of the unix basename command can be unearthed. The automaton will
search for
^.[^j]*jr.*$
on standard input. And the program which results by running adgrep.c
through this filter requires two parameters. The first is meant to be a
filename, and the second, an extension. All leading pathname components
are removed from the filename, and the extension is removed if present.
The resulting base name is printed to stdout.
Lastly, by setting the first line to
/* . sleep . */
you can search for
^.[^(~][^s]*sl.*$
Filtering adgrep.c through this search yields a clone of the sleep
command. Invoke with a single integer parameter, and it will pause
for that many seconds.
If either adbasename or adsleep is invoked with too few parameters,
the program will print the error message:
> Segmentation fault (core dumped)
(The exact text of the above error messages varies from machine to
machine.) The four programs which read from stdin require lines
shorter than 999 characters.
The other info files are adrian.grep.[1-6] which contain the six
examples that appear above, and from, which is used to emulate the
unix from command. For reasons of clarity, the name "from" should
probably not be changed if possible. I wouldn't want to be accused of
confusing people by giving the input files weird names.
If you want to change the default input filename (line 80) you must be
careful to choose a name that doesn't match the wrong search patterns,
introducing extra lines into one of the programs.
The program will produce at least one warning and possible several
when compiled depending on the compiler.
## Copyright and CC BY-SA 4.0 License:
1992/adrian/adrian.c
+1 -2
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@@ -7,7 +7,6 @@
#define v(jr) jr
int W ,head;
#define S(W,b,f) strncpy(W,b,f),W[f]=0\
char *wcs=" \t\n";
struct{ char X[z+1];
@@ -105,7 +104,7 @@ while( s = strtok(0,wcs)) {
< 10 && printf((W,Y)); }
if(j+28) { {
; } printf("%7u%7u%7u\n", wcl , wcw , wcc); }
while( gets(Y) ) if(A(Y)) puts(Y);
while( fgets(Y,998,stdin) ){ Y[strlen(Y)-1]='\0'; if(A(Y)) puts(Y); }
W, jr; }
O(int wc,char**V) {