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--- internal:administration:idl [2025/07/20 13:19] – [execute shell command] jan
+++ internal:administration:idl [2025/11/25 14:42] (current) – [symboltypes] jan
@@ Line 195: / Line 195: @@
   IDL> spawn, 'curl -V'
   curl: /opt/nv5/idl90/bin/bin.linux.x86_64/libcurl.so.4: no version information available (required by curl)
-  curl 8.5.0 (x86_64-pc-linux-gnu) libcurl/8.4.0-DEV OpenSSL/3.0.11 zlib/1.2.13 zstd/1.5.5 nghttp2/1.58.0
+  ...
-  Release-Date: 2023-12-06, security patched: 8.5.0-2ubuntu10.6
-  Protocols: dict file ftp ftps gopher gophers http https imap imaps mqtt pop3 pop3s rtsp smb smbs smtp smtps telnet tftp
-  Features: alt-svc AsynchDNS HSTS HTTP2 HTTPS-proxy IPv6 Largefile libz NTLM SSL threadsafe TLS-SRP UnixSockets zstd
   WARNING: curl and libcurl versions do not match. Functionality may be affected.
-The first line and the last lines tell you that %%libcurl.so.4%% from the %%/opt/nv5/idl90/...%% path makes problems.
+The first and the last lines tell you that %%libcurl.so.4%% from the %%/opt/nv5/idl90/...%% path makes problems.
+But why should curl try to load libraries from /opt/nv5/... i.e. the IDL folder ?
-Another axample is ghostscript (gs) - which not even work:
+Another example is ghostscript (gs) - which does not even work:
   IDL> SPAWN, 'gs --version'
   gs: /opt/nv5/idl90/bin/bin.linux.x86_64/libstdc++.so.6: version `GLIBCXX_3.4.32' not found (required by /lib/x86_64-linux-gnu/libgs.so.10)
-To get around you have to adapt the environment variable LD_LIBRARY_PATH . It is not present in standard bash environment but is set by IDL to access is own set of libraries, and remains valid in the SPAWN environment. We have two possibilities:
+Again ghostscript tries to load lubraries from /opt/nv5/...
-  * adapt from within IDL (but maybe IDL will have problems with that ...)
-    SETENV, 'LD_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu/:'+GETENV('LD_LIBRARY_PATH')
+To get around you have to understand where the system seeks libraries.
-  * Alternatively adapt within the SPAWN environment when calling your program
+This is explained e.g. here: [[https://askubuntu.com/questions/1500913/find-default-library-paths-location-in-ubuntu]], or in the man pages of [[https://man7.org/linux/man-pages/man8/ld.so.8.html | ld.so]]. To ensure that IDL only uses libraries of a certain version they set the variable LD_LIBRARY_PATH to the idl library folders. It is not set in standard bash environment, but in the SPAWN environment as it is a subrpocess of IDL:
-    SPAWN, 'LD_LIBRARY_PATH=/usr/lib:$LD_LIBRARY_PATH; '+your_command_here
+  IDL> SPAWN, 'echo $LD_LIBRARY_PATH'
-The first solution is a bit dangerous as it may lead to incompatbilities within IDL.
+  /opt/nv5/idl90/bin/bin.linux.x86_64:/opt/nv5/idl90/bin/bin.linux.x86_64/dm/lib:/opt/nv5/idl90/bin/bin.linux.x86_64/jre/lib/server:/opt/nv5/idl90/bin/bin.linux.x86_64/jre/lib/server/..:/opt/nv5/idl90/bin/bin.linux.x86_64/jre/lib/server/../native_threads
+We can ask Linux where we can find the libraries needed:
+  $whereis libcurl.so.4
+  libcurl.so.4: /usr/lib/x86_64-linux-gnu/libcurl.so.4
+and
+  $whereis libstdc++.so.6
+  libstdc++.so.6: /usr/lib/x86_64-linux-gnu/libstdc++.so.6
+We have several possibilities:
+  * adapt the LD_LIBRARY_PATH from within IDL before invoking SPAWN. This was proposed to me : [[https://www.nv5geospatialsoftware.com/Support/Forums/aft/8650 in the IDL forum]] for the PAtH variable but maybe IDL will have problems with that. And you should do this only once to avoid an extremly long path with only your prepended entry.
+      %%SETENV, 'LD_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu/:'+GETENV('LD_LIBRARY_PATH')%%
+  * Alternatively adapt LD_LIBRARY_PATH within the SPAWN environment when calling your program
+      %%SPAWN, 'LD_LIBRARY_PATH=/usr/lib:$LD_LIBRARY_PATH; your_command_here'%%
+  * or even simpler unset this path variable in SPAWN: it is not needed as we are not doing IDL specific things, and when SPAWN is finished this is forgotten again.
+      %%SPAWN, 'unset LD_LIBRARY_PATH; your_command_here'%%
+According to IDL help about [[https://www.nv5geospatialsoftware.com/docs/Environment_Variables.html | Environment variables]] LD_LIBRARY_PATH is used for the Java libraries - i.e. probably for the IDE and its graphical interface. That means if you do not use the IDE the first solution will have no problems.
 Check with curl:
-    SPAWN, 'LD_LIBRARY_PATH=/usr/lib:$LD_LIBRARY_PATH; curl -V'
+    SPAWN, 'unset LD_LIBRARY_PATH ; curl -V'
     curl 8.5.0 (x86_64-pc-linux-gnu) libcurl/8.5.0 OpenSSL/3.0.13 zlib/1.3 brotli/1.1.0 zstd/1.5.5 libidn2/2.3.7 libpsl/0.21.2 (+libidn2/2.3.7) libssh/0.10.6/openssl/zlib nghttp2/1.59.0 librtmp/2.3 OpenLDAP/2.6.7
-    Release-Date: 2023-12-06, security patched: 8.5.0-2ubuntu10.6
+    ...
-    Protocols: dict file ftp ftps gopher gophers http https imap imaps ldap ldaps mqtt pop3 pop3s rtmp rtsp scp sftp smb smbs smtp smtps telnet tftp
-    Features: alt-svc AsynchDNS brotli GSS-API HSTS HTTP2 HTTPS-proxy IDN IPv6 Kerberos Largefile libz NTLM PSL SPNEGO SSL threadsafe TLS-SRP UnixSockets zstd
 Check with ghostscript
-    SPAWN, ''LD_LIBRARY_PATH=/usr/lib:$LD_LIBRARY_PATH; gs --version'
+    SPAWN, 'unset LD_LIBRARY_PATH ; gs --version'
 .02.1
+=> WORKS!
 ==== compile and run idl programs ====
@@ Line 1828: / Line 1845: @@
 => Plus sign (+)
 => Asterisk (*)
-=> Period (.)
+=> one pixel dot (.)
 => Diamond
-=> Triangle 'up'
+=> Triangle up (if symsize>0)  or down if symsize<0
 => Square
 => X
@@ Line 2488: / Line 2505: @@
 ==== transparency ====
-IDL does not know transparent overlays but on pixel based devices you can implement it with TVRD and TVRD.
+IDL does not know transparent overlays but on pixel based devices you can implement it with TVRD and TV.
 Lets assume you want to put a bitmap BMP with size Nx, Ny at a position x0 y0 (pixels) with a tranparency factor of q_tra:
@@ Line 2657: / Line 2674: @@
 %%-dGraphicsAlphaBits=1%% avoids gridlines after rastering (http://www.idlcoyote.com/ps_tips/psstripes.html), \\
 %%-dEPSCrop%% crops the image at the bounding box.
+You can execute gs from within IDL with the SPAWN command. As of IDL 9.x you need to prepend a ''unset LD_LIBRARY_PATH'' because IDL try to ensure its own (outdated) libraries for any spawn call:
+  SPAWN, 'unset LD_LIBRARY_PATH; gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r120 -dTextAlphaBits=4 -dGraphicsAlphaBits=1 -dEPSCrop -sOutputFile='+plt_name+'.png '+pl_name+'.eps', result, err_result
 ==== postscript -> PDF ====
@@ Line 3227: / Line 3248: @@
 A one dimensional histogram is e.g. generated with
-  histo = histogram( data , binsize=bin, locations = classes , /nan )
+  binsize = 0.1
+  histo = histogram( data , binsize=binsize, locations = classes , /nan )
 the classes variable will contain the **lower borders** of the bins with the first bin starting at min(data). \\
@@ Line 3246: / Line 3268: @@
 or you write an own plot-histo procedure ... or you ask jan :-) ...
+A histogram with geometric spacing, i.e. each bin is by a factor q_bin larger than the previous.\\
+In this case data points lower or equal to zero are not allowed:
+  q_bin = 2.0
+  log_binsize = alog10(q_bin)
+  histo = histogram( alog10(data[where(data gt 0)]), binsize=log_binsize, locations = log_bins, /nan )
+  classes = 10^log_bins
+Plotting shall use then logarithmic scaling for the x-axes:
+    plot, classes , histo , psym=10, $
+      xtitle = 'class (unit)', $
+      ytitle = 'freq.', $
+      /xlog
 === 2-D histogram ===
@@ Line 3256: / Line 3294: @@
   max_data_1 = max(data_1, /nan )
   N_bins_1 = fix((max_data_1-min_data_1)/bin_size_1)+1
-  bins_1 = min_data_1 + (findgen(N_bins_1) + 0.5) * bin_size_1 ; output of histo refers to lower border of bins => add 1/2binsize to center them in bin
+  ; output of histo refers to lower border of bins => add 1/2binsize to center them in bin
+  bins_1 = min_data_1 + (findgen(N_bins_1) + 0.5) * bin_size_1
   ; set bin-size, min and max and vector with bin-borders for data set 2
@@ Line 3263: / Line 3302: @@
   max_data_2 = max(data_2, /nan )
   N_bins_2 = fix((max_data_2-min_data_2)/bin_size_2)+1
+  ; output of histo refers to lower border of bins => add 1/2binsize to center them in bin
   bins_2 = min_data_2 + (findgen(N_bins_2) + 0.5)*bin_size_2