I want to execute the very simple command
print var1, var2, var3, var4
in gdb to examine the values of the vars from time to time.
I don't want to use display because it clutters up my view.
How can I do this? Right now all I can do is:
p var1
p var2
p var3
p var4
You can simply do this
print {var1,var2,var3,var4}
This will do the job.
Use the printf command. It's a bit of a hassle, but it gives good control over the formatting. From the command line:
(gdb) help printf
printf "printf format string", arg1, arg2, arg3, ..., argn
This is useful for formatted output in user-defined commands.
The format string is like in C (%d for normal size ints, %s for null terminated strings, etc.).
Use Macros:
For example to continue to next break point and print
(gdb) define prm
Type commands for definition of prm.
End with a line saying just end.
>continue
>print var1
>print var2
>print var3
>end
(gdb) prm
$5 = 0
$6 = 10
$7 = -1
There may be a simpler solution, but you might be able to put together something using GDB macros: http://www.ibm.com/developerworks/aix/library/au-gdb.html
Related
In .gdbinit I call to function
call open("tmp/test",1)
Then I got return value
$15 = 1
I want to use $15 to the next operation.
How can I got this var to the .gdbinit next line ?
You can simply assign the return value to a variable with a name of your choosing:
(gdb) call $ret = open("tmp/test", 1)
(gdb) print $ret
-1
By default, using p variable-name will display $num = variable-value, $num is the value history, but it there a way to print the variable name along with the variable value like $num = variable-name = variable-value?
I want this since I use
define p
set $i = 0
while $i < $argc
eval "print $arg%d", $i
set $i = $i + 1
end
end
in my ~/.gdbinit, to redefine p command so I can use p var1 var2 var3... to print multiple variables at once, but the print command only output $num = variable-value, and I don't know what the exact variable is in the output, the other situation is when I print the value history using just p $num, it is not that readable, I don't know the exact variable name.
NOTE: the variable may be int/char/pointer/array/vector/...
A solution could be to first add to the display list the wanted variables and then to display all of them together. Note that, it is needed to free the display list before with undisplay, otherwise it also prints the variables of the previous executions.
define p
set confirm off
eval "undisplay"
set confirm on
set $i = 0
while $i < $argc
eval "display $arg%d", $i
set $i = $i + 1
end
display
end
The undisplay evaluation is enclosed between set confirm off/on to suppress the following message:
[answered Y; input not from terminal]
If you have already set the confirm off option in your ~/gdbinit file, you will need to remove these two lines.
Edit: Honestly, I came to know about the display command finding a solution for this question. Although this answer might be useful to print multiple variables with their respective names, after several days using display in my workflow, I discourage to use this answer since I have come to the conclusion that display itself fits better at least my needs (printing multiple variables at every stop). Here the official doc:
If you find that you want to print the value of an expression frequently (to see how it changes), you might want to add it to the automatic display list so that GDB prints its value each time your program stops. Each expression added to the list is given a number to identify it; to remove an expression from the list, you specify that number. The automatic display looks like this:
2: foo = 38
3: bar[5] = (struct hack *) 0x3804
Basically, I have started using the command like this: I add a variable with display $var to the list of variables, and every time a breakpoint is reached the listed variables are automatically printed. It makes sense to have a feature like this in gdb. Thanks #CodyChan for the motivation.
In a nutshell, we want to output
$num = variable-name = variable-value
instead of
$num = variable-value
As far as I can tell, gdb adds to the value history in only three places: the print command, the call command, and the history-append! Scheme function. Since my Scheme is rusty, we'll need to use the CLI or Python to run print and modify its output.
Using the CLI
define pp
set $i = 0
while $i < $argc
eval "pipe print $arg%d | awk -v name='$arg%d' '{ if (NR == 1 && $2 == \"=\") { $2 = \"= \" name \" =\" }; print }'", $i, $i
set $i++
end
end
Pipe is new in gdb 10.
That awk command is, after unescaping,
awk -v name='$arg%d' '{ if (NR == 1 && $2 == "=") { $2 = "= " name " =" }; print }'
which changes the = (second field) in $num = variable-value to = variable-name = . If gdb's print command outputs more than one line, the NR == 1 in the awk command makes sure the substitution is only done on the first line.
Security note: gdb's pipe command appears to parse the shell_command into tokens and uses execve to run it, rather than passing it to an actual shell. This prevents some code injection attacks (if, for instance, the $arg%d in name='$arg%d' contains single quotes), but you should be careful of running any shell command comprised of text you haven't vetted.
Using Python
class PP(gdb.Command):
"""print value history index, name, and value of each arg"""
def __init__(self):
super(PP, self).__init__("pp", gdb.COMMAND_DATA, gdb.COMPLETE_EXPRESSION)
def invoke(self, argstr, from_tty):
for arg in gdb.string_to_argv(argstr):
line = gdb.execute("print " + arg, from_tty=False, to_string=True)
line = line.replace("=", "= " + arg + " =", 1)
gdb.write(line)
PP()
Here, we're using a more sed-like approach, using string.replace.
Sample session:
(gdb) set args a b c
(gdb) start
Starting program: /home/mp/argprint a b c
Temporary breakpoint 2, main (argc=4, argv=0x7ffffffee278) at argprint.c:4
4 for(int i=0; i < argc; i++) {
(gdb) pp i argc argv argv[0]#argc
$1 = i = 0
$2 = argc = 4
$3 = argv = (char **) 0x7ffffffee278
$4 = argv[0]#argc = {0x7ffffffee49f "/home/mp/argprint", 0x7ffffffee4b1 "a", 0x7ffffffee4b3 "b", 0x7ffffffee4b5 "c"}
The below code doesn't seem to be working for the variable all_s when there is more than 1 record with the same urn. Var1,2,3 work fine but that one doesn't and I cant figure out why. I am trying to have all_s equal to single_var1,2,3 concatenated with no spaces if it's first.urn but I want it to be
all_s = all_s + ',' + single_var1 + single_var2 + single_var3
when it's not the first instance of that urn.
data dataset_2;
set dataset_1;
by URN;
retain count var1 var2 var3 all_s;
format var1 $40. var2 $40. var3 $40. all_s $50.;
if first.urn then do;
count=0;
var1 = ' ';
var2 = ' ';
var3 = ' ';
all_s = ' ';
end;
var1 = catx(',',var1,single_var1);
var2 = catx(',',var2,single_var2);
var3 = catx(',',var3,single_var3);
all_s = cat(all_s,',',single_var1,single_var2,single_var3);
count = count+1;
if first.urn then do;
all_s = cat(single_var1,single_var2,single_var3);
end;
run;
all_s is not large enough to contain the concatenation if the total length of the var1-var3 values within the group exceeds $50. Such a scenario seems likely with var1-var3 being $40.
I recommend using the length function to specify variable lengths. format will create a variable of a certain length as a side effect.
catx removes blank arguments from the concatenation, so if you want spaces in the concatenation when you have blank single_varN you won't be able to use catx
A requirement that specifies a concatenation such that non-blank values are stripped and blank values are a single blank will likely have to fall back to the old school trim(left(… approach
Sample code
data have;
length group 8 v1-v3 $5;
input group (v1-v3) (&);
datalines;
1 111 222 333
1 . 444 555
1 . . 666
1 . . .
1 777 888 999
2 . . .
2 . b c
2 x . z
run;
data want(keep=group vlist: all_list);
length group 8 vlist1-vlist3 $40 all_list $50;
length comma1-comma3 comma $2;
do until (last.group);
set have;
by group;
vlist1 = trim(vlist1)||trim(comma1)||trim(left(v1));
vlist2 = trim(vlist2)||trim(comma2)||trim(left(v2));
vlist3 = trim(vlist3)||trim(comma3)||trim(left(v3));
comma1 = ifc(missing(v1), ' ,', ',');
comma2 = ifc(missing(v2), ' ,', ',');
comma3 = ifc(missing(v3), ' ,', ',');
all_list =
trim(all_list)
|| trim(comma)
|| trim(left(v1))
|| ','
|| trim(left(v2))
|| ','
|| trim(left(v3))
;
comma = ifc(missing(v3),' ,',',');
end;
run;
Reference
SAS has operators and multiple functions for string concatenation
|| concatenate
cat concatenate
catt concatenate, trimming (remove trailing spaces) of each argument
cats concatenate, stripping (remove leading and trailing spaces) of each argument
catx concatenate, stripping each argument and delimiting
catq concatenate with delimiter and quote arguments containing the delimiter
From SAS 9.2 documentation
Comparisons
The results of the CAT, CATS, CATT, and CATX functions are usually equivalent to results that are produced by certain combinations of the concatenation operator (||) and the TRIM and LEFT functions. However, the default length for the CAT, CATS, CATT, and CATX functions is different from the length that is obtained when you use the concatenation operator. For more information, see Length of Returned Variable.
Note: In the case of variables that have missing values, the concatenation produces different results. See Concatenating Strings That Have Missing Values.
Some example data would be helpful, but I'm going to give it a shot and ask you to try
all_s = cat(strip(All_s),',',single_var1,single_var2,single_var3);
I have two variables var1 and var2 on two different line numbers. My task is:
To open an input file, search for the lines beginning with var1 and insert a comment ABOVE the line.
To open the same input file, search for the lines beginning with var2 and insert a comment BELOW the line.
I was able to achieve 1 but not 2.
var1 = 2 #line number
var2 = 5 #line number
comment1 = "inserted text above var1"
comment2 = "inserted text below var2"
some for loop:
found1 = False
found2 = False
for line in fileinput.input(source.txt, inplace=True):
if not found and line.startswith(var1):
print comment1
found1 = True
print line,
if not found and line.startswith(var2):
print line
found1 = True
print comment2,
Input File:
1 abc
2 def
3 ghi
4 jkl
5 mno
6 pqr
7 stu
Output should be :
1 abc
inserted text above var1
2 def
3 ghi
4 jkl
5 mno
inserted text below var2
6 pqr
7 stu
You seem to have a lot of variables that you don't need. The way that I read your code, based on the indenting, you'll always print comment2, and sometimes you'll print the line more then once.
You do not need 2 for loops. You don't ever use found1 or found2, and the variable found is never defined these are variables that you probably don't need. You either need to define source.txt as a variable, or pass it as a string(put " around it, which is what I think you meant to do). var1, and var2 should probably be strings as well, since str.startswith() expects a string to be passed in.
Simplify it a little and I think you wont have a problem. Assuming that you are handling the reading the file correctly, something like this should do the trick.
var1= "2" #line number
var2 = "5" #line number
comment1 = "inserted text above var1"
comment2 = "inserted text below var2"
for line in fileinput.input("source.txt", inplace=True):
if line.startswith(var1):
print comment1
print line
if line.starswith(var2):
print comment2
What I want is this :
(gdb) define mynext
Redefine command "mynext"? (y or n) y
Type commands for definition of "mynext".
End with a line saying just "end".
>print "------"
>print Location:
>where
>print "-------------"
>print Code:
>list
>print "---------------------"
>print Next:
>next
>end
This is what outputs is:
$1 = "-----"
....
I expect:
-----
....
I used call printf("opopo") also, but It print the return value of "opopo" which is 5. Just like this:$4 = 5
My question is: how can I print something without this format which is :$[num]=[value].
As you found, print puts the printed value into the value history. gdb provides two different ways to avoid this.
One is printf. This works somewhat like the C function, but is a gdb command. Use it like:
(gdb) printf "whatever you like\n"
whatever you like
(gdb)
Another is output. This is a bit like the print command, but does not enter the value into the value history.
(gdb) output 5
5(gdb)
You can see from this that output also doesn't emit a trailing newline. You would have to add that yourself.